Project plan updates:
- Mark all 14 Phase 3 tasks as completed
- Update acceptance criteria to met
- Update master plan status to Phase 4 next
- Add detailed deliverables list for Phase 3
Documentation updates:
- Add UNSET sentinel pattern to CLAUDE.md
- Document when to use UNSET vs None for nullable fields
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>