run_features() fills the foundation2 stub: librosa beat/tempo tracking +
onset-strength detection at a 10 ms hop (librosa's default 32 ms grid at
16 kHz quantizes past the +/-50 ms acceptance bound), tempo from the median
inter-beat interval, times mapped to t_global via the frozen timebase
helpers. Degradation per house style: missing videos/WAV -> summary with
note, nothing written; silent/short/beatless audio -> valid-empty
beats.json, never a crash.
Acceptance (test_audio_features.py, 7 tests): synthetic 120 BPM grid
recovered — tempo 120.0 (+/-2 required), worst beat 30 ms off grid
(+/-50 required); the three ground-truth bangs appear as strong onsets;
silence/short/missing all degrade cleanly; CLI dispatch end-to-end.
CR-4: minimal stub-era assertion updates in test_phase5_api.py (CLI stub
loop shrinks to capsule) per the approved CR-1 precedent — see
plan/CHANGE_REQUESTS.md.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
