feat: add advisory docs sync review for pull requests

[rishabhraj36]

Description

Adds an advisory documentation-sync review for pull requests.

The workflow checks whether user-facing changes are reflected in README.md, docs/, and bundled skills/. Obvious non-documentation changes are resolved deterministically; relevant code and documentation changes receive a Gemini review. Results are advisory and never block merging.

Maintainers can apply the docs-not-needed label when no update is required.

Closes #72

Type of Change

• ✨ New feature
• 📝 Documentation
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Adapter Notes

• Updated generated or lean docs when command discoverability changed
• Used positional args for the command's primary subject unless a named flag is clearly better
• Normalized expected adapter failures to CliError subclasses instead of raw Error

Screenshots / Output

No UI changes. Verification completed with the full test suite and TypeScript typecheck.

[rishabhraj36]

🟢 No documentation gap found — low confidence

The pull request introduces a new CI workflow for documentation synchronization review and updates `CONTRIBUTING.md` to describe this process. The changes are primarily internal tooling and contributor-facing, and the relevant documentation (`CONTRIBUTING.md`) has been updated. No user-facing behavior of the `webcmd` tool itself has changed, so `README.md`, `docs/`, or `skills/` do not require updates.

Limitations

• Review context was truncated.

Source: gemini.

This review is advisory and does not block merging.