fix: a second copy of a track counts once, joining words don't part two titles, and a newer matcher retries an older one's refusals (M502 #5569)

The second run's refusals were mostly albums holding a track twice (a
two-track single with three files), which no edition can pair, and
release names that differ only in "+" against "/". Tracks are now read
once per disc, number and title, and "and", "&" and "+" count for nothing
when titles are compared; an edition's own title also counts as the
album's name.

library_album_matches records which matcher version decided each album.
Refusals by an older version are matched again, even after the listing is
done, so an improvement reaches them without a migration.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/wanted/library.go

@@ -23,6 +23,15 @@ const libraryMatchBudget = 2 * time.Minute
 // libraryMatchBatch is how many albums one query hands the matching.
 const libraryMatchBatch = 25
 
+// libraryMatcher is the matching's version. Raise it when the matching
+// changes in a way that could match an album it refused: albums an older
+// version refused are matched again, even after the listing is done.
+//
+//	1  tags, release, discography and search, checked by title and length
+//	2  titles alone under the album's own name; a refusal names the track
+//	3  a second copy of a track counts once; joining words count for nothing
+const libraryMatcher = 3
+
 // listLibrary puts the library's albums on the wanted list as held, once
 // (operator, 2026-10-10: "make a record saying that the import has
 // happened so later changes like unwanting hold and dont auto import from
@@ -39,7 +48,8 @@ const libraryMatchBatch = 25
 //     of the albums no match was found for.
 //
 // Each album decided is recorded in library_album_matches, so an album taken
-// off the list stays off, and once done the listing never runs again.
+// off the list stays off. Once done the listing runs again only for albums
+// an older matcher refused (libraryMatcher).
 func (s *Service) listLibrary(ctx context.Context, res *PassResult) error {
 	q := dbq.New(s.pool)
 	state, err := q.GetLibraryListing(ctx)
@@ -47,7 +57,13 @@ func (s *Service) listLibrary(ctx context.Context, res *PassResult) error {
 		return fmt.Errorf("wanted: read the library listing: %w", err)
 	}
 	if state.LibraryListedAt.Valid {
-		return nil
+		stale, err := q.CountAlbumsToRematch(ctx, libraryMatcher)
+		if err != nil {
+			return fmt.Errorf("wanted: count refusals to retry: %w", err)
+		}
+		if stale == 0 {
+			return nil
+		}
 	}
 	cutoff := state.LibraryListingStartedAt
 	if !cutoff.Valid {
@@ -67,7 +83,8 @@ func (s *Service) listLibrary(ctx context.Context, res *PassResult) error {
 
 	deadline := s.now().Add(libraryMatchBudget)
 	for {
-		albums, err := q.ListAlbumsToMatch(ctx, dbq.ListAlbumsToMatchParams{Cutoff: cutoff, MaxRows: libraryMatchBatch})
+		albums, err := q.ListAlbumsToMatch(ctx, dbq.ListAlbumsToMatchParams{
+			Cutoff: cutoff, Matcher: libraryMatcher, MaxRows: libraryMatchBatch})
 		if err != nil {
 			return fmt.Errorf("wanted: albums to match: %w", err)
 		}
@@ -107,7 +124,8 @@ func (s *Service) listAlbum(ctx context.Context, q *dbq.Queries, a dbq.ListAlbum
 	}
 	if !m.OK {
 		s.logger.Info("wanted: no MusicBrainz match for a library album", "album", a.Title, "artist", a.ArtistName, "why", m.Detail)
-		return 0, q.RecordAlbumMatch(ctx, dbq.RecordAlbumMatchParams{AlbumID: a.ID, Outcome: "unmatched", Detail: m.Detail})
+		return 0, q.RecordAlbumMatch(ctx, dbq.RecordAlbumMatchParams{
+			AlbumID: a.ID, Outcome: "unmatched", Detail: m.Detail, Matcher: libraryMatcher})
 	}
 	var listed int64
 	err = pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
@@ -124,7 +142,7 @@ func (s *Service) listAlbum(ctx context.Context, q *dbq.Queries, a dbq.ListAlbum
 		}
 		listed = n
 		return tq.RecordAlbumMatch(ctx, dbq.RecordAlbumMatchParams{
-			AlbumID: a.ID, Outcome: "listed", Method: m.Method, ReleaseGroupMbid: m.Group,
+			AlbumID: a.ID, Outcome: "listed", Method: m.Method, ReleaseGroupMbid: m.Group, Matcher: libraryMatcher,
 		})
 	})
 	if err != nil {