docs: update CLAUDE.md with architecture details and type safety guidelines

- Update build/dev mode descriptions to reflect current feature flags
- Add workspace packages table and multi-API compatibility layer docs
- Add Type Safety Guidelines section: prohibit `as any` in non-test code,
  document proper alternatives (Record<string, unknown>, dual assertion,
  type guards, specific SDK types)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: claude-code-best