CI: Add Claude-powered documentation philosophy check

[oldsj]

Summary

Add a CI check that uses Claude to enforce our documentation philosophy:

README.md → docs/ → specs/ → tests/

Behavior

• Trigger: Every PR
• On failure: Fail the build (block merge)

What to Verify

1. Features documented in README have corresponding entries in docs/
2. Docs reference specs that define the behavior
3. Specs have corresponding e2e tests that verify the behavior
4. Tests match what specs describe

Implementation Ideas

• Use Claude in a GitHub Action to analyze PR changes
• Check for documentation completeness across the chain
• Provide actionable feedback when docs are missing or out-of-sync
• Could use Claude Code CLI or Anthropic API directly

Acceptance Criteria

• CI runs on every PR
• Fails with clear message when documentation chain is broken
• Suggests what documentation needs to be added/updated