Update dev containers documentation to reflect GA status (v2.24.0+) and
fix various inaccuracies identified in PR #18907.

Key changes:

User guides (docs/user-guides/devcontainers/):
- Rewrite SSH section with correct agent-based access patterns
- Remove deprecated --container flag examples
- Add native port forwarding to sub-agents as primary method
- Fix prerequisites to note Docker + devcontainers CLI requirements
- Clarify that discovery is on by default but autostart is off
- Expand troubleshooting guide with Docker, agent naming, and
  connection issues

Admin docs:
- Rename devcontainers/ folder to envbuilder/ to clarify it's an
  alternative approach
- Add notes recommending native Dev Containers integration
- Fix module registry URLs (dev.registry -> registry.coder.com)
- Update links to prioritize native integration over Envbuilder

Also adds .markdownlint-cli2.jsonc to ignore PLAN.md in linting.

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies from limited implementation knowledge. The main issues
were:

- SSH examples used the deprecated --container flag instead of the
  agent-based access pattern (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is off
  by default (discovery is on, but containers don't auto-start)

The Envbuilder docs were in a folder called "devcontainers" which
caused confusion about which approach was primary. Renamed to
"envbuilder" and added notes recommending native Dev Containers for
most use cases.

Also fixes registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

PR #18907 attempted to update the dev containers docs but was closed due
to inaccuracies. The main issues were:

- SSH examples used the deprecated --container flag instead of
  agent-based access (coder ssh workspace.agent)
- Port forwarding focused on appPort when native forwarding to
  sub-agents is the primary method
- Prerequisites implied users needed to "enable" Dev Containers when
  it's on by default—the real requirements are Docker and the CLI
- The "automatic build" section was misleading since autostart is
  off by default (discovery finds configs, users click to start)

Changes made:

User guides (docs/user-guides/devcontainers/):
- Rewrote SSH and port forwarding sections with correct patterns
- Fixed prerequisites to reflect actual requirements
- Moved Features list before Getting Started for better flow
- Simplified working-with doc to focus on practical steps
- Rewrote troubleshooting with verified, actionable content

Admin docs:
- Renamed devcontainers/ to envbuilder/ to clarify it's an alternative
- Added notes recommending native Dev Containers integration
- Fixed module registry URLs (dev.registry -> registry.coder.com)
- Added Alternative section to envbuilder docs for symmetry

Refs #18907

PR #18907 attempted to update these docs but was closed due to
inaccuracies from limited implementation knowledge.

The SSH examples used the deprecated --container flag instead of the
agent-based pattern (coder ssh workspace.agent). Port forwarding
focused on appPort configuration when native forwarding directly to
sub-agents is the primary method. Prerequisites implied users needed
to "enable" Dev Containers when it's actually on by default—the real
requirements are just Docker and the devcontainers CLI.

The "automatic build" section implied containers start automatically,
but autostart is off by default. Discovery finds devcontainer.json
files and shows them in the UI; users click to start unless the admin
configured autostart.

Renamed the admin docs folder from devcontainers/ to envbuilder/ since
it documents Envbuilder specifically, not native Dev Containers. This
caused confusion about which approach was recommended. Added notes
pointing to native Dev Containers as the recommended approach for most
use cases, with Envbuilder as an alternative for Docker-less
environments.

Also fixes module registry URLs that pointed to dev.registry instead
of registry.coder.com.

The admin template configuration docs (extending-templates/devcontainers.md)
were recently rewritten and remain mostly unchanged beyond the registry
URL fix.

Refs #18907

PR #18907 attempted to update these docs but was closed due to
inaccuracies from limited implementation knowledge.

The SSH examples used the deprecated --container flag instead of the
agent-based pattern (coder ssh workspace.agent). Port forwarding
focused on appPort configuration when native forwarding directly to
sub-agents is the primary method. Prerequisites implied users needed
to "enable" Dev Containers when it's actually on by default—the real
requirements are just Docker and the devcontainers CLI.

The "automatic build" section implied containers start automatically,
but autostart is off by default. Discovery finds devcontainer.json
files and shows them in the UI; users click to start unless the admin
configured autostart.

Renamed the admin docs folder from devcontainers/ to envbuilder/ since
it documents Envbuilder specifically, not native Dev Containers. This
caused confusion about which approach was recommended. Added notes
pointing to native Dev Containers as the recommended approach for most
use cases, with Envbuilder as an alternative for Docker-less
environments.

Also fixes module registry URLs that pointed to dev.registry instead
of registry.coder.com.

The admin template configuration docs (extending-templates/devcontainers.md)
were recently rewritten and remain mostly unchanged beyond the registry
URL fix.

Refs #18907

PR #18907 attempted to update these docs but was closed due to
inaccuracies from limited implementation knowledge.

The SSH examples used the deprecated --container flag instead of the
agent-based pattern (coder ssh workspace.agent). Port forwarding
focused on appPort configuration when native forwarding directly to
sub-agents is the primary method. Prerequisites implied users needed
to "enable" Dev Containers when it's actually on by default—the real
requirements are just Docker and the devcontainers CLI.

The "automatic build" section implied containers start automatically,
but autostart is off by default. Discovery finds devcontainer.json
files and shows them in the UI; users click to start unless the admin
configured autostart.

Renamed the admin docs folder from devcontainers/ to envbuilder/ since
it documents Envbuilder specifically, not native Dev Containers. This
caused confusion about which approach was recommended. Added notes
pointing to native Dev Containers as the recommended approach for most
use cases, with Envbuilder as an alternative for Docker-less
environments.

Also fixes module registry URLs that pointed to dev.registry instead
of registry.coder.com.

The admin template configuration docs (extending-templates/devcontainers.md)
were recently rewritten and remain mostly unchanged beyond the registry
URL fix.

Refs #18907

PR #18907 attempted to update these docs but was closed due to
inaccuracies from limited implementation knowledge.

The SSH examples used the deprecated --container flag instead of the
agent-based pattern (coder ssh workspace.agent). Port forwarding
focused on appPort configuration when native forwarding directly to
sub-agents is the primary method. Prerequisites implied users needed
to "enable" Dev Containers when it's actually on by default—the real
requirements are just Docker and the devcontainers CLI.

The "automatic build" section implied containers start automatically,
but autostart is off by default. Discovery finds devcontainer.json
files and shows them in the UI; users click to start unless the admin
configured autostart.

Renamed the admin docs folder from devcontainers/ to envbuilder/ since
it documents Envbuilder specifically, not native Dev Containers. This
caused confusion about which approach was recommended. Added notes
pointing to native Dev Containers as the recommended approach for most
use cases, with Envbuilder as an alternative for Docker-less
environments.

Also fixes module registry URLs that pointed to dev.registry instead
of registry.coder.com.

The admin template configuration docs (extending-templates/devcontainers.md)
were recently rewritten and remain mostly unchanged beyond the registry
URL fix.

Refs #18907

PR #18907 attempted to update these docs but was closed due to
inaccuracies from limited implementation knowledge.

The SSH examples used the deprecated --container flag instead of the
agent-based pattern (coder ssh workspace.agent). Port forwarding
focused on appPort configuration when native forwarding directly to
sub-agents is the primary method. Prerequisites implied users needed
to "enable" Dev Containers when it's actually on by default—the real
requirements are just Docker and the devcontainers CLI.

The "automatic build" section implied containers start automatically,
but autostart is off by default. Discovery finds devcontainer.json
files and shows them in the UI; users click to start unless the admin
configured autostart.

Renamed the admin docs folder from devcontainers/ to envbuilder/ since
it documents Envbuilder specifically, not native Dev Containers. This
caused confusion about which approach was recommended. Added notes
pointing to native Dev Containers as the recommended approach for most
use cases, with Envbuilder as an alternative for Docker-less
environments.

Also fixes module registry URLs that pointed to dev.registry instead
of registry.coder.com.

The admin template configuration docs (extending-templates/devcontainers.md)
were recently rewritten and remain mostly unchanged beyond the registry
URL fix.

Refs #18907

PR #18907 attempted to update these docs but was closed due to
inaccuracies from limited implementation knowledge.

The SSH examples used the deprecated --container flag instead of the
agent-based pattern (coder ssh workspace.agent). Port forwarding
focused on appPort configuration when native forwarding directly to
sub-agents is the primary method. Prerequisites implied users needed
to "enable" Dev Containers when it's actually on by default—the real
requirements are just Docker and the devcontainers CLI.

The "automatic build" section implied containers start automatically,
but autostart is off by default. Discovery finds devcontainer.json
files and shows them in the UI; users click to start unless the admin
configured autostart.

Renamed the admin docs folder from devcontainers/ to envbuilder/ since
it documents Envbuilder specifically, not native Dev Containers. This
caused confusion about which approach was recommended. Added notes
pointing to native Dev Containers as the recommended approach for most
use cases, with Envbuilder as an alternative for Docker-less
environments.

Also fixes module registry URLs that pointed to dev.registry instead
of registry.coder.com.

The admin template configuration docs (extending-templates/devcontainers.md)
were recently rewritten and remain mostly unchanged beyond the registry
URL fix.

Refs #18907

… for GA

The previous documentation had inaccuracies: SSH examples used the
deprecated `--container` flag instead of the agent-based pattern
(`coder ssh workspace.agent`), port forwarding focused on `appPort` when
native forwarding to sub-agents is the primary method, and prerequisites
implied users needed to "enable" dev containers when it is on by default.

Renamed admin docs folder from `devcontainers/` to `envbuilder/` since it
documents Envbuilder specifically, not native dev containers. Added notes
pointing to native dev containers as the recommended approach for most
use cases.

Also fixes module registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

The previous documentation had inaccuracies: SSH examples used the
deprecated `--container` flag instead of the agent-based pattern
(`coder ssh workspace.agent`), port forwarding focused on `appPort` when
native forwarding to sub-agents is the primary method, and prerequisites
implied users needed to "enable" dev containers when it is on by default.

Renamed admin docs folder from `devcontainers/` to `envbuilder/` since it
documents Envbuilder specifically, not native dev containers. Added notes
pointing to native dev containers as the recommended approach for most
use cases.

Also fixes module registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

The previous documentation had inaccuracies: SSH examples used the
deprecated `--container` flag instead of the agent-based pattern
(`coder ssh workspace.agent`), port forwarding focused on `appPort` when
native forwarding to sub-agents is the primary method, and prerequisites
implied users needed to "enable" dev containers when it is on by default.

Renamed admin docs folder from `devcontainers/` to `envbuilder/` since it
documents Envbuilder specifically, not native dev containers. Added notes
pointing to native dev containers as the recommended approach for most
use cases.

Also fixes module registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

The previous documentation had inaccuracies: SSH examples used the
deprecated `--container` flag instead of the agent-based pattern
(`coder ssh workspace.agent`), port forwarding focused on `appPort` when
native forwarding to sub-agents is the primary method, and prerequisites
implied users needed to "enable" dev containers when it is on by default.

Renamed admin docs folder from `devcontainers/` to `envbuilder/` since it
documents Envbuilder specifically, not native dev containers. Added notes
pointing to native dev containers as the recommended approach for most
use cases.

Also fixes module registry URLs that pointed to dev.registry instead of
registry.coder.com.

Refs #18907

docs: rewrite dev containers documentation for GA

Corrects inaccuracies in SSH examples (deprecated `--container` flag),
port forwarding (native sub-agent forwarding is primary), and
prerequisites (dev containers are on by default). Fixes template
descriptions: docker-devcontainer uses native Dev Containers while
AWS/Kubernetes templates use Envbuilder.

Renames admin docs folder from `devcontainers/` to `envbuilder/` to
reflect actual content. Adds customization guide documenting agent
naming, display apps, custom apps, and variable interpolation. Documents
multi-repo workspace support and adds note about Terraform module
limitations with sub-agents. Fixes module registry URLs.

Refs #18907

docs: rewrite dev containers documentation for GA

Corrects inaccuracies in SSH examples (deprecated `--container` flag),
port forwarding (native sub-agent forwarding is primary), and
prerequisites (dev containers are on by default). Fixes template
descriptions: docker-devcontainer uses native Dev Containers while
AWS/Kubernetes templates use Envbuilder.

Renames admin docs folder from `devcontainers/` to `envbuilder/` to
reflect actual content. Adds customization guide documenting agent
naming, display apps, custom apps, and variable interpolation. Documents
multi-repo workspace support and adds note about Terraform module
limitations with sub-agents. Fixes module registry URLs.

Refs coder#18907