Fix typecheck: addMessage/findById now require userId (from PR #293). Mark M2-001/002/005/006 done. All Wave 1 tasks complete (9/65). PRs #290, #292, #293, #294 merged. Issues #224-226, #232-237 closed. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>