Documents the 4 stacked regressions in test_mma_concurrent_tracks_sim
that need a proper fix. Not sweeping under the rug - the test was passing
in some prior state but the cruft_elimination_20260627 changes (commit
0d2a9b5e and related) broke multiple consumers without updating them.
Fixes already in (a4901fa2, 635ca552):
- flat.setdefault(...)[...] = ... on frozen ProjectContext (3 sites)
- t_data['id'] on Ticket objects (1 site)
- mock_concurrent_mma.py --resume handling
Remaining: 1 critical failure where the second track's _start_track_logic
never fires. Recommend a dedicated track to investigate + fix.
