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/components/play-in-context.test.ts

@@ -0,0 +1,271 @@
+/**
+ * Playing a track plays the list it is in.
+ *
+ * Double-clicking a row — or picking Play from its context menu — used
+ * to call `SetQueue([thatOnePath], 0)` on the album page, in the track
+ * list and in the two playlist views' menus: the queue became one
+ * track, the rest of the album was discarded, and playback stopped at
+ * the end of it. What a player means by activating a row is "start
+ * here", and the here is a position in the list on screen.
+ *
+ * So the queue is the *displayed* list and `startIndex` is the row.
+ * Two rules ride along and are what these tests are mostly for:
+ *
+ * - The album page's list is the tracks it has files for, so the index
+ *   is into that and not into the tracklist that includes the dimmed
+ *   rows — off-by-however-many-you-do-not-own is silent, it just plays
+ *   the wrong song.
+ * - A menu asks how much is selected. One row means "from here"; an
+ *   explicit multi-row selection means play exactly those, which is
+ *   the one case where a queue of the selection is what was asked for.
+ */
+import { describe, expect, it, beforeEach } from 'vitest';
+import type { LitElement } from 'lit';
+
+import '@components/explore-album-details/explore-album-details';
+import '@components/track-list/track-list';
+import '@components/playlist-details/playlist-details';
+import { stub, flush, resetHarness, lastArgs } from '@test/support/harness';
+import { fixture, shadowAll } from '@test/support/render';
+
+/** What `Queue.SetQueue` was last asked to play, and from where. */
+function queued(): { paths: string[]; startIndex: number } {
+  const args = lastArgs('queue.Queue.SetQueue');
+
+  if (!args) throw new Error('nothing was queued');
+
+  return {
+    paths: args[0] as string[],
+    startIndex: args[1] as number,
+  };
+}
+
+function dblclick(el: Element): void {
+  el.dispatchEvent(
+    new MouseEvent('dblclick', { bubbles: true, composed: true }),
+  );
+}
+
+// =====================================================================
+// The album page
+// =====================================================================
+
+function albumTrack(n: number, owned: boolean) {
+  return {
+    position: n,
+    discNumber: 1,
+    title: `Track ${n}`,
+    length: 200000,
+    mbid: `mbid-${n}`,
+    inLibrary: owned,
+  };
+}
+
+/**
+ * A release on the page without the network, owned every `nth` track.
+ * The fixture says which tracks have *files*, because that is the one
+ * question the page asks about ownership.
+ */
+async function album(total: number, ownedMbids: string[]): Promise<LitElement> {
+  const el = await fixture<LitElement>('explore-album-details', {
+    albumName: 'Glass Harbour',
+  });
+
+  const tracks = Array.from({ length: total }, (_, i) =>
+    albumTrack(i + 1, ownedMbids.includes(`mbid-${i + 1}`)),
+  );
+
+  const paths: Record<string, string[]> = {};
+  for (const mbid of ownedMbids) paths[mbid] = [`/music/${mbid}.mp3`];
+
+  stub('library.Library.GetFilePathsByRecordingMBIDs', paths);
+
+  Object.assign(el, {
+    versionEntries: [
+      { key: 'v1', label: '2019', sublabel: `${total} tracks`, tracks },
+    ],
+    selectedVersionKey: 'v1',
+    loadingReleases: false,
+    loadingInfo: false,
+  });
+  el.requestUpdate();
+  await flush();
+  await el.updateComplete;
+
+  return el;
+}
+
+describe('double-clicking a track on the album page', () => {
+  beforeEach(() => {
+    resetHarness();
+    stub('library.Library.GetFilePathsByAlbums', {});
+    stub('library.Library.GetAlbumTracks', []);
+    stub('library.Library.GetAllLibrariesWithTrackCounts', []);
+  });
+
+  it('queues the album and starts on that track', async () => {
+    const el = await album(6, ['mbid-1', 'mbid-2', 'mbid-3', 'mbid-4', 'mbid-5', 'mbid-6']);
+
+    dblclick(shadowAll(el, '.track-row')[2]!);
+    await flush();
+
+    expect(queued()).toEqual({
+      paths: [1, 2, 3, 4, 5, 6].map((n) => `/music/mbid-${n}.mp3`),
+      startIndex: 2,
+    });
+  });
+
+  it('indexes into what is owned, not into the rows on screen', async () => {
+    // Tracks 2, 5 and 6 have files; the other three rows are dimmed and
+    // are not in the queue at all. Row 5 is therefore the *second*
+    // thing that will play, and an index taken from the row would start
+    // this album past its end.
+    const el = await album(6, ['mbid-2', 'mbid-5', 'mbid-6']);
+
+    dblclick(shadowAll(el, '.track-row')[4]!);
+    await flush();
+
+    expect(queued()).toEqual({
+      paths: ['/music/mbid-2.mp3', '/music/mbid-5.mp3', '/music/mbid-6.mp3'],
+      startIndex: 1,
+    });
+  });
+
+  it('does nothing at all on a row with no file behind it', async () => {
+    const el = await album(6, ['mbid-2']);
+
+    dblclick(shadowAll(el, '.track-row')[0]!);
+    await flush();
+
+    expect(lastArgs('queue.Queue.SetQueue')).toBeUndefined();
+  });
+});
+
+// =====================================================================
+// The track list
+// =====================================================================
+
+const LIST = Array.from({ length: 12 }, (_, i) => ({
+  FilePath: `/music/track-${i}.mp3`,
+  TrackName: `Track ${i}`,
+  ArtistName: 'An Artist',
+  Album: 'An Album',
+  Duration: 180,
+})) as never[];
+
+describe('double-clicking a row in the track list', () => {
+  let el: LitElement;
+
+  beforeEach(async () => {
+    resetHarness();
+    localStorage.removeItem('track-list-column-widths');
+
+    el = await fixture<LitElement>('track-list', { externalTracks: LIST });
+    el.style.display = 'block';
+    el.style.height = '600px';
+    await flush();
+    await el.updateComplete;
+    await new Promise((r) => setTimeout(r, 60));
+  });
+
+  it('queues the list as displayed and starts on that row', async () => {
+    const rows = shadowAll(el, '.track-row');
+    const row = rows.find((r) => r.getAttribute('data-index') === '3');
+
+    dblclick(row!);
+    await flush();
+
+    const { paths, startIndex } = queued();
+
+    expect([paths.length, paths[startIndex]]).toEqual([
+      12,
+      '/music/track-3.mp3',
+    ]);
+  });
+});
+
+// =====================================================================
+// A playlist's context menu
+// =====================================================================
+
+function playlistTracks(n: number) {
+  return Array.from({ length: n }, (_, i) => ({
+    ID: i + 1,
+    FilePath: `/music/track-${i}.mp3`,
+    Title: `Track ${i}`,
+    Artist: 'An Artist',
+    Album: 'An Album',
+    Duration: 180000,
+    Phantom: false,
+  }));
+}
+
+describe('Play from a playlist row’s context menu', () => {
+  let el: LitElement;
+
+  beforeEach(async () => {
+    resetHarness();
+    stub('playlist.Service.GetPlaylistTracks', playlistTracks(8));
+    stub('playlist.Service.GetAllPlaylists', []);
+
+    el = await fixture<LitElement>('playlist-details', {
+      playlistId: 1,
+      playlistName: 'A playlist',
+    });
+    el.style.display = 'block';
+    el.style.height = '600px';
+    await flush();
+    await el.updateComplete;
+    await new Promise((r) => setTimeout(r, 60));
+  });
+
+  /** Right-click a row, then click the menu's Play item. */
+  async function playFromMenu(index: number): Promise<void> {
+    const row = shadowAll(el, '.track-item').find(
+      (r) => r.getAttribute('data-index') === String(index),
+    );
+
+    row!.dispatchEvent(
+      new MouseEvent('contextmenu', { bubbles: true, composed: true }),
+    );
+    await el.updateComplete;
+
+    const items = shadowAll<HTMLElement>(el, 'wa-dropdown-item');
+    const play = items.find((i) => i.textContent?.trim().startsWith('Play') &&
+      !i.textContent.includes('Next'));
+
+    play!.click();
+    await flush();
+  }
+
+  it('starts the playlist from the row that was clicked', async () => {
+    await playFromMenu(5);
+
+    const { paths, startIndex } = queued();
+
+    expect([paths.length, startIndex]).toEqual([8, 5]);
+  });
+
+  it('plays only the selection when several rows are selected', async () => {
+    // The one case where a queue of the selection is what was asked
+    // for: the user said which tracks, not where to start.
+    const rows = shadowAll(el, '.track-item');
+    const click = (i: number, modifiers: MouseEventInit) =>
+      rows
+        .find((r) => r.getAttribute('data-index') === String(i))!
+        .dispatchEvent(
+          new MouseEvent('click', { bubbles: true, composed: true, ...modifiers }),
+        );
+
+    click(1, {});
+    click(4, { ctrlKey: true });
+    await el.updateComplete;
+
+    await playFromMenu(4);
+
+    expect(queued().paths).toEqual([
+      '/music/track-1.mp3',
+      '/music/track-4.mp3',
+    ]);
+  });
+});