User report: SoulSync was only pulling MusicBrainz genres from the
recording (track-level) endpoint. Most MB recordings don't carry genres
at the track level — they live on the release (album) or artist. So
the MB tier was contributing nothing to the genre merge for the
overwhelming majority of tracks.
Fix:
- Added `'genres'` to the release-detail `includes` (was missing).
- After release-detail processing, if pp['mb_genres'] is still empty,
populate from release_detail['genres'] (sorted by count desc).
- If still empty AND artist_mbid is set, fetch artist with
`includes=['genres']` and use those.
No extra API call when the recording (or release) already had genres —
the artist fetch only fires when both upstream tiers came back empty.
The downstream genre merge in _embed_metadata_genres is unchanged; this
just makes the MB feed into it richer.
Tests: 4 new (recording present, recording empty → release, recording
+ release empty → artist, all empty → []). Full suite 873 passing.
Ruff clean.
Reported by @kcaoyef421 in Discord.
c121582557