Multi-artist surfaces (home Rediscover, Library Artists tab, Liked
Artists carousel) were all rendering the music-notes placeholder
instead of real artist covers. Root cause:
CachedArtist.toRef() returned an ArtistRef with empty coverUrl —
the cache doesn't store the representative album id the server
derives at query time, and the adapter never reconstructed it.
The artist detail screen worked coincidentally because it derives
its header cover from `artist.albums[0].id` directly rather than
the ArtistRef's coverUrl field.
Fix:
* CachedArtistAdapter.toRef() now accepts an optional coverAlbumId
and reconstructs `/api/albums/<id>/cover` when given. Matches the
pattern AlbumRef uses (deterministic URL from entity id).
* artistTileProvider, libraryArtistsProvider, and artistProvider
(single-artist) each LEFT JOIN cached_albums ordered by sort_title.
First row per artist carries the alphabetically-first album id;
toRef projects that into the cover URL.
* Multi-artist queries dedup in toResult since the join multiplies
rows by album count.
Artists with no albums yet in drift come through with empty
coverUrl — UI falls back to the music-notes placeholder, same
behavior as before for that legitimately-coverless state.
bvandeusen
8cb9a8b797