fall._states, immobility._still_since/_fired, zone._inside_since/_fired,
and engine._last_emit were never pruned when a track was lost (ghost
already pruned via on_lost). On a 24/7 edge device this is unbounded
growth as track IDs keep incrementing.
Add forget(track_id) to FallDetector, ImmobilityWatchdog, and
ZoneIntrusionDetector (drops that track's per-track keys/sets).
EventEngine.forget(track_id) calls each sub-detector's forget and removes
_last_emit cooldown keys whose tuple's second element is that track_id
(covers FALL/NO_MOTION/IMMOBILITY/zone/GHOST — GHOST keys are
(GHOST, track_id) after FIX 4). EventEngine.process now calls
self.forget(tr.track_id) for every track in lost_tracks after emitting,
since ghost.on_lost already consumed that track's ghost-relevant state at
the top of process().
app.py run_once already calls pool.forget(tr.track_id) for lost tracks as
part of FIX 1, completing the cleanup chain (smoother pool + detector
state + dedup cache).
Tests: tests/test_engine.py adds test_forget_prunes_state_on_lost —
fires a FALL event, then passes the track as lost, and asserts
engine._last_emit no longer has that track's keys and fall._states no
longer has the track id.
edge/detectors/fall.py update(): a single frame where prone was false while
state was in {FALLING, FALLEN, NO_MOTION} immediately emitted "recover" and
reset _State. One jittery frame (a momentary pose-estimation miss) could
wipe an in-progress CRITICAL no_motion incident.
Add FallConfig.recover_grace_s (default 1.0s) and _State.not_prone_since.
On the first non-prone frame while in an incident state, start the grace
timer instead of recovering immediately; only reset to STANDING once
recover_grace_s of sustained non-prone has elapsed. A re-prone frame while
in an incident state clears the pending grace timer (cancels the recover
attempt). The non-incident STANDING path is unchanged.
BEHAVIOR CHANGE: recover now requires recover_grace_s of sustained
non-prone instead of firing on a single frame.
Tests: test_recovery_clears_state (tests/test_fall.py) strengthened per
review brief to assert a single standing frame does NOT recover but
sustained standing across the grace window does. Added
test_single_noisy_nonprone_frame_does_not_cancel_no_motion covering the
life-safety scenario: one noisy non-prone frame during NO_MOTION must not
cancel the incident.
