Merges feature/tracker-registry. See e9aea3f for the detail; in summary the
tracker no longer owns track state, association weights embedding over position
whenever position is uninformative, and every similarity comparison is a
calibrated probability.
Four constants retired: track_max_embed_dist, cut_revive_sim,
cut_inactive_max_frames, track_max_frames_missing.
Suite: 80 cases, 3250 assertions.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
TRACES: AR-007, AR-008, AR-024 | SR-002