feat(database): shape the library like files, and shrink the catalog

Plans 013 and 014, the album page that prompted them, and the smaller
fixes they turned up. Changelog, largest first.

## The local library is shaped like files, not like MusicBrainz

`audio_files` carries its own tags and points at `albums` and
`artists`; `file_genres` is the one real many-to-many. `recordings`,
`release_group_recordings`, `artist_credit`, `artist_credit_artist`,
`recording_genres`, `release_groups` and `release_to_rg` are gone from
the local side, and with them a six-way join in every read, a
`MIN(release_group_id)` subquery in eleven queries and a
first-credited-artist subquery in nine. Measured on a real 25,966-file
library, every many-to-many that model expressed was 1:1 in the data.

- Ownership is a file. `GetFilePathsByRecordingMBIDs`,
  `LibraryMBIDIndex.CheckMBIDs`, `collectLibraryEntities` and
  `pruneStaleLocalCrossReferences` all join `audio_files`, so the 812
  orphaned recordings, 216 release groups and 260 artists that library
  carried are now structurally impossible.
- One projection: every track query selects from the `track_metadata`
  view, one row type, one mapper. Nine hand-rolled copies had drifted
  far enough to report different years on different screens.
- `library_id = 0` means every library, so each list query exists once
  instead of scoped and unscoped with a branch at every call site.
- No migration chain. `sql/schemas/` is the one description of the
  shape; `sql/migrations/`, `applyMigrations` and `schema_migrations`
  are squashed away, along with the drift between them that had sqlc
  generating against a stale schema.
- `database.InsertTestTrack` is the one test seeder; twenty test files
  had been assembling the old FK chain each in its own order.

## The catalog stores its ids as bytes

`explore_index`'s three 36-char MBID columns and its entity-type text
are 16 raw bytes and a small integer. The table and its six indexes go
780 MB to 405 MB on a real 2,052,200-row catalog, which is why a fresh
install is ~0.6 GB rather than ~1.0 GB.

- `backend/explore/mbid.go` is the only place the encoding is known;
  everything above it speaks dashed strings.
- `CHECK(length(mbid) = 16)` makes a stringly write fail at the insert
  rather than silently returning no rows, since SQLite does not coerce
  between TEXT and BLOB.
- The importer asks the artifact what encoding it carries and converts
  on the way in, so the artifact already published keeps working and no
  format bump is needed.
- `indexRowColumns`/`scanIndexRow` replace four copies of a 22-column
  list, and `TestStoredEncodingRoundTrips` sweeps every read path.

## An album page that says how much of the album is yours

- One question, asked once: is there a file. `filePaths` is filled by a
  single batched lookup when the tracklist settles, and the badge, the
  Play count, the dimmed rows and every menu item read it — replacing
  four claims of decreasing confidence that could show a green tick on
  an album whose every action did nothing.
- Play, Play 7 of 12, or no play button at all.
- `total_tracks` on `explore_index` (~2 bytes over 400,677 release
  groups) and on `audio_files` from tags that have always carried it:
  a complete MBID-matched album now makes no catalog call at all, where
  it used to spend the most expensive request the app makes.
- A merged cluster shows the running order the most releases agree on,
  and the version list marks the release you own rather than standing a
  synthetic entry in for it.
- `AlbumReleasesFailed`: a slow fetch is no longer reported as a failed
  one by a 12-second timer.
- Rows not in the library are dimmed in place (with `aria-disabled`)
  instead of the owned ones wearing a green tick and a legend.

## Caches and cover art get ceilings

- Only the three tiers of a cover are stored; the full-resolution copy
  nothing rendered was 1,134 MB of a 1.4 GB covers directory.
- One artist portrait is downloaded and the rest are remembered as
  URLs — 4.1 GB of a 5.3 GB cache was candidates no code path reads.
- `browsedArtBudget` and `httpCacheBudget` bound what an age cannot:
  the same install held art for 5,770 artists in a 1,301-artist
  library.
- `OrphanedArtistImagesJob` joined a bare MBID onto a sharded
  directory, so it deleted the rows that were the only record of the
  files it left behind. `explore.ArtistImageDir` is that layout's one
  definition now.

## The autotag queue asks whether there is work

`tagging_items` was a row per album folder, not a queue, and no query
read the `tag_status` column that held the answer. The four queue
queries ask the files, which matters most where it is least visible:
`startPrefetch` was scoring every album in a tagged library against
MusicBrainz.

## Phantom playlist tracks resolve in place

An M3U8 imported before its files leaves phantom rows; they now match
by path and fall back to position, keep their place in the playlist
when resolved, and pair best-first so two phantoms cannot claim the
same file.

## Playing a track plays the list it is in

Double-click, and Play on a single row's menu, queue the list as
displayed with `startIndex` on that row — the album page and the track
list used to queue one track and discard the album around it. A
multi-row selection still plays exactly itself.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AfVYUVExXsx1nSWrXN8mAh

frontend/test/stores/library-store.test.ts

@@ -33,16 +33,16 @@ const LIBRARIES = [{ id: 7, name: 'Music' }, { id: 8, name: 'Field' }];
 /** Stub every read binding the store can reach. Unstubbed bindings
  *  resolve undefined, which the store would cache as if it were data. */
 function stubReads(): void {
-  stub('library.Library.GetAllTracks', TRACKS);
-  stub('library.Library.GetAllAlbums', ALBUMS);
-  stub('library.Library.GetAllArtists', ARTISTS);
-  stub('library.Library.GetAllGenresWithCounts', GENRES);
-  stub('library.Library.GetAllTracksByLibrary', TRACKS);
-  stub('library.Library.GetAllAlbumsByLibrary', ALBUMS);
-  stub('library.Library.GetAllArtistsByLibrary', ARTISTS);
-  stub('library.Library.GetAllGenresWithCountsByLibrary', GENRES);
+  stub('library.Library.GetTracks', TRACKS);
+  stub('library.Library.GetAlbums', ALBUMS);
+  stub('library.Library.GetArtists', ARTISTS);
+  stub('library.Library.GetGenres', GENRES);
+  stub('library.Library.GetTracks', TRACKS);
+  stub('library.Library.GetAlbums', ALBUMS);
+  stub('library.Library.GetArtists', ARTISTS);
+  stub('library.Library.GetGenres', GENRES);
+  stub('library.Library.GetAlbumsByArtist', ALBUMS);
   stub('library.Library.GetAlbumsByArtist', ALBUMS);
-  stub('library.Library.GetAlbumsByArtistByLibrary', ALBUMS);
   stub('library.Library.GetAllLibrariesWithTrackCounts', LIBRARIES);
 }
 
@@ -69,7 +69,7 @@ describe('library store: caching', () => {
   it('serves a second read from cache without touching the backend', async () => {
     await libraryStore.getTracks();
 
-    expect(calls('library.Library.GetAllTracks')).toHaveLength(0);
+    expect(calls('library.Library.GetTracks')).toHaveLength(0);
   });
 
   it('deduplicates concurrent first reads into one backend call', async () => {
@@ -79,7 +79,7 @@ describe('library store: caching', () => {
       libraryStore.getArtists(),
     ]);
 
-    expect([a, b, calls('library.Library.GetAllArtists').length]).toEqual([
+    expect([a, b, calls('library.Library.GetArtists').length]).toEqual([
       ARTISTS,
       ARTISTS,
       1,
@@ -100,10 +100,10 @@ describe('library store: caching', () => {
     await flush();
 
     expect(calls().map((c) => c.path).sort()).toEqual([
-      'library.Library.GetAllAlbums',
-      'library.Library.GetAllArtists',
-      'library.Library.GetAllGenresWithCounts',
-      'library.Library.GetAllTracks',
+      'library.Library.GetAlbums',
+      'library.Library.GetArtists',
+      'library.Library.GetGenres',
+      'library.Library.GetTracks',
     ]);
   });
 
@@ -111,7 +111,7 @@ describe('library store: caching', () => {
     emit(Events.TrackMetadataChanged, { filePath: '/a.mp3' });
     await flush();
 
-    expect(calls('library.Library.GetAllTracks')).toHaveLength(1);
+    expect(calls('library.Library.GetTracks')).toHaveLength(1);
   });
 
   /*
@@ -192,7 +192,7 @@ describe('library store: caching', () => {
     });
 
     it('does not refetch the tracks', () => {
-      expect(calls('library.Library.GetAllTracks')).toHaveLength(0);
+      expect(calls('library.Library.GetTracks')).toHaveLength(0);
     });
 
     it('splices the removed track out in place', () => {
@@ -204,9 +204,9 @@ describe('library store: caching', () => {
     it('reloads the summaries, whose counts changed', () => {
       expect(
         [
-          'library.Library.GetAllAlbums',
-          'library.Library.GetAllArtists',
-          'library.Library.GetAllGenresWithCounts',
+          'library.Library.GetAlbums',
+          'library.Library.GetArtists',
+          'library.Library.GetGenres',
         ].map((path) => calls(path).length),
       ).toEqual([1, 1, 1]);
     });
@@ -258,7 +258,7 @@ describe('library store: library filter', () => {
     libraryStore.setSelectedLibrary(7);
     await flush();
 
-    expect(lastArgs('library.Library.GetAllTracksByLibrary')).toEqual([7]);
+    expect(lastArgs('library.Library.GetTracks')).toEqual([7]);
   });
 
   it('ignores a redundant selection instead of invalidating', async () => {
@@ -284,10 +284,10 @@ describe('library store: library filter', () => {
 
   it('scopes an artist drill-down to the selected library', async () => {
     libraryStore.setSelectedLibrary(8);
-    await libraryStore.getAlbumsByArtist(3);
+    await libraryStore.getAlbumsByArtist('Artist');
 
-    expect(lastArgs('library.Library.GetAlbumsByArtistByLibrary')).toEqual([
-      3, 8,
+    expect(lastArgs('library.Library.GetAlbumsByArtist')).toEqual([
+      'Artist', 8,
     ]);
   });
 });
@@ -309,7 +309,7 @@ describe('library store: a fetch that is overtaken', () => {
     // Only the track fetch is held open; the other three settle at once,
     // so the test is about the overtaking and nothing else.
     stub(
-      'library.Library.GetAllTracksByLibrary',
+      'library.Library.GetTracks',
       (id: number) =>
         new Promise((resolve) => {
           pending.push({ id, resolve });
@@ -331,7 +331,7 @@ describe('library store: a fetch that is overtaken', () => {
   });
 
   it('settles the waiters when the fetch they are waiting on fails', async () => {
-    stubFailure('library.Library.GetAllTracks', 'sql: database is locked');
+    stubFailure('library.Library.GetTracks', 'sql: database is locked');
     // Invalidation drops the cache and starts the fetch that fails.
     emit(Events.LibraryScanComplete);
 
@@ -447,7 +447,7 @@ describe('library store: albums by artist name', () => {
   });
 
   it('filters the album cache by artist name', () => {
-    stub('library.Library.GetAllAlbums', [...ALBUMS, ...OTHER_ALBUMS]);
+    stub('library.Library.GetAlbums', [...ALBUMS, ...OTHER_ALBUMS]);
 
     expect(libraryStore.getAlbumsByArtistNameCached('Artist')).toEqual(ALBUMS);
   });