A MusicBrainz album resolves its art at RELEASE-GROUP scope even for a concrete
release (musicbrainz_search _release_to_album -> _cached_art prefers the rg mbid).
On the Cover Art Archive a release-group front is a single REPRESENTATIVE cover
(CAA picks one release to stand for the group, ~always the standard edition), so
a special edition like "Clair Obscur: Expedition 33 (Gustave Edition)" got the
standard art baked into cover.jpg + embedded tags at download time.
Add core/metadata/caa_art.fetch_release_preferred_art: try the specific release
own /release/<mbid>/front first, fall back to the existing release-group/provider
URL only when the release has no art of its own (404 -> None). Wire it into both
download_cover_art (cover.jpg) and embed_album_art_metadata (tags) so they stay
in sync. min_bytes defaults to 0 so the fallback keeps its prior behavior — this
can only ever ADD a better edition match, never strip a cover that showed before.
Caveat (documented, not fixed here): this only helps when the resolved release IS
the right edition. If the upstream match picked the standard release/group, that
is the separate canonical-version matching problem.
Tests: pure helper (prefers release art, falls back on 404/tiny/exception, no-mbid
passes through, nothing-available -> None). 667 metadata/artwork/deezer/hifi tests pass.
