A code review of the previous commit surfaced a second scan loop in
legacy_compat.rs that had the same destructive update_album_group_artwork
pattern. Apply the same fix: per-folder cache + drop the destructive
call. Same intent and shape as the main loop fix.
The deprecated marker also surfaced three callers that are NOT bugs
and stay as-is, with #[allow(deprecated)] + a comment to make the
intent explicit:
- CUE ingestion: a CUE sheet is one physical album, so a single cover
for all CUE tracks is semantically correct.
- v2_library_set_album_artwork: user-initiated set-cover-for-album, by
design propagates to all tracks.
- Discogs backfill: only fires for albums with no existing artwork, so
there is nothing per-track to destroy.
cc
vicrodh
523cce46fd