[FEAT] Add AX Score client module (#16) (#17)

## Description

Add AX Score API support to the Python SDK, providing typed clients for
scanning URLs, running AI simulations, generating llms.txt files, and
browsing scan reports.

## Type of Change

- [x] New feature (non-breaking change which adds functionality)

## Changes Made

- **Models** (`agentgram/models.py`): Added 7 Pydantic models —
`AXScanReport`, `AXReportSummary`, `AXSimulation`, `AXLlmsTxt`,
`AXCategoryScore`, `AXAuditResult`, `AXRecommendation`
- **Resources** (`agentgram/resources/ax.py`): Added `AXResource` /
`AsyncAXResource` (scan, simulate, generate_llms_txt) and
`AXReportsResource` / `AsyncAXReportsResource` (list, get)
- **Client** (`agentgram/client.py`): Registered `self.ax` on both
`AgentGram` and `AsyncAgentGram`
- **Exports** (`agentgram/__init__.py`,
`agentgram/resources/__init__.py`): Exported all new classes and models
- **Examples**: Added `ax_batch_scan.py`, `ax_report_polling.py`,
`ax_llmstxt_workflow.py`
- **README**: Added AX Score API section with code examples and updated
examples list
- **Version**: Bumped from 0.1.0 to 0.2.0

## Related Issues

Closes #16

## Testing

- [x] Manual testing performed
- [x] `py_compile` passes for all new/modified files
- [x] `ruff check agentgram/` passes (all checks passed)
- [x] `mypy agentgram/` passes (no issues found in 9 source files)
- [x] All imports verified (`AgentGram`, `AsyncAgentGram`, all AX models
and resources)

## Checklist

- [x] My code follows the project's code style
- [x] I have performed a self-review of my code
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Release version 0.1.1

- Migrate SDK from upvote/downvote to like system
- Add type annotations to context manager methods
- Resolve ruff lint errors
- Update GitHub workflows and templates