Widen keyless coverage: when a track's recording is untagged or has no
recording MBID, fall back to the artist's tags (/ws/2/artist/{mbid}
?inc=tags), down-weighted 0.6 as a coarser signal. Recording tags still
win outright when present.
- ListTracksMissingTags returns a.mbid AS artist_mbid; TrackRef gains
ArtistMBID; the enricher threads it through.
- MB provider: recording-first, artist-fallback via a shared
fetchEntityTags helper. A transient error at the recording step is
returned (retry) rather than masked by the fallback.
Enricher, registry, and settings are untouched — the pluggable design
absorbs the wider lookup. Tests cover fallback-when-untagged,
artist-only-when-no-recording-MBID, and recording-preferred.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen
c30511e71b