Document the vibe coding pattern (LLM generates code, E2B sandbox
executes it, user sees live preview) using Fragments as the reference
implementation. Add navigation entry and home page card.

Switch imports from plain e2b to @e2b/code-interpreter to match
Fragments' actual usage. Clarify that the app runs outside the
sandbox, using it purely to prepare and serve the generated code.

Replace verbose How It Works section with a Why E2B bullet list.
Merge dependency and code-writing sections. Trim code examples
to focus on the essential API calls.