Completes Task 3 on top of the recovered wip checkpoint (be8f24b4):
- fix the programmatically-generated MP3 fixture's frame length: lofty's
Header::read computes samples*bitrate*125/sample_rate with truncating
integer division BEFORE adding the padding byte, so the FF FB 52 C4
frame is 209 bytes, not 210 — the off-by-one made cmp_header miss the
second frame sync and reject the whole file as containing an invalid
frame (mp3_id3v24_yields_full_record now passes; fixture-only fix,
production code untouched)
- all 7 music::tags tests green; no binary audio fixtures committed
(fixtures are built byte-by-byte into tempdirs at test run time)
- extract_tags canonicalizes and confines to caller-supplied media_roots
before opening any file (T-13-20); non-audio is a distinct NotAudio
error vs the Ok/has_tags=false untagged fallback (T-13-21)
- entity types in music/mod.rs implement 13-MUSIC-MODEL.md exactly:
hybrid-identity TrackId, derived albums/artists, MUSIC_SCHEMA_VERSION=1
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
