Comprehensive 12-section completion report following the format of
TRACK_COMPLETION_ai_loop_regressions_20260615.md. Documents:
- 4 atomic commits, 1288+4+0 fully green baseline
- 2 defensive guards in src/rag_engine.py (lines 150 and 331)
- 3 new unit tests in tests/test_rag_sync_none_error.py
- 4 plan deviations (spec wrong about root cause, test_rag_visual_sim
was already passing, traceback diagnostic was a dead end, temp dir
cleanup retry loop for Windows)
- 5 followup recommendations for Tier 1 review