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/src/utils/queue-source-link.ts

@@ -8,8 +8,17 @@
  * the destinations and attributes differ per source type, and there is
  * no MBID/local-id fallback dance to share — a queue source always
  * carries a local id (`tracks` is the one exception, needing none).
+ *
+ * An album is the one source that needs more than its local id.
+ * `explore-album-details` is a *catalog* page and decides what it is
+ * showing from `release-group-mbid` alone — with only a local id it
+ * says "library only" about an album that is perfectly well tagged,
+ * which is not what the same album opened from the albums grid says.
+ * So the MBID is read off the library row here, exactly as
+ * `cover-grid` reads it off the card it navigates from.
  */
 
+import { libraryStore } from '../store/library-store';
 import type { QueueSource } from '../store/queue-store';
 
 /** Fire a navigate event from the clicked element. */
@@ -75,6 +84,26 @@ export function describeQueueSource(source: QueueSource): string | null {
     return `Playing from ${source.label}`;
 }
 
+/**
+ * The release-group MBID of a library album, or '' when it has none.
+ *
+ * Reads the album cache synchronously when it is warm — the albums
+ * view populates it, and so does anything else that has asked for the
+ * collection — and only awaits a fetch when nothing has yet.
+ */
+function albumMBID(id: number): string | Promise<string> {
+    const find = (albums: readonly { ID: number; MBID: string }[]): string =>
+        albums.find((a) => a.ID === id)?.MBID ?? '';
+
+    const cached = libraryStore.cachedAlbums;
+    if (cached) return find(cached);
+
+    return libraryStore
+        .getAlbums()
+        .then(find)
+        .catch(() => '');
+}
+
 /** Navigate to the collection a queue was built from. */
 export function navigateToQueueSource(
     target: EventTarget,
@@ -83,5 +112,25 @@ export function navigateToQueueSource(
     const buildDetail = SOURCE_NAVIGATE_DETAIL[source.type];
     if (!buildDetail) return;
 
-    navigate(target, buildDetail(source));
+    const detail = buildDetail(source);
+
+    if (source.type !== 'album') {
+        navigate(target, detail);
+
+        return;
+    }
+
+    const mbid = albumMBID(source.id);
+
+    if (typeof mbid === 'string') {
+        if (mbid) detail.releaseGroupMBID = mbid;
+        navigate(target, detail);
+
+        return;
+    }
+
+    void mbid.then((resolved) => {
+        if (resolved) detail.releaseGroupMBID = resolved;
+        navigate(target, detail);
+    });
 }

frontend/src/utils/track-details-opener.ts

@@ -0,0 +1,77 @@
+/**
+ * Open `<track-details>` for a file path.
+ *
+ * The five library-side hosts already hold the `library.Track` the
+ * dialog wants — they render it. Explore's rows do not: a tracklist row
+ * is an `MBTrack`/`LBTopRecording` from the catalog, and all it can say
+ * about the library is *which file is behind it*. So the path is the
+ * one key both sides share, and turning it back into a track is the
+ * work this does.
+ *
+ * `libraryStore.getTracks()` is awaited rather than
+ * `getCachedTracks()`-and-bail (which is what `queue-panel` does):
+ * Explore is reachable without ever opening the library views, so a
+ * cold cache is ordinary here rather than a symptom, and silently doing
+ * nothing on a menu item the user just clicked is not an option. The
+ * fetch is the store's own, shared with every other reader.
+ */
+
+import type * as library from '@go/library/models.js';
+import type {
+    CoverArtUrls,
+    TrackDetails,
+} from '@components/track-details/track-details.js';
+import { libraryStore } from '@store/library-store.js';
+import { loadTrackDetails } from '@utils/lazy-track-details.js';
+import { tracksByFilePath } from '@utils/track-index.js';
+
+/** The cover art the dialog shows, or nothing when the track has none. */
+function coverArtOf(track: library.Track): CoverArtUrls | undefined {
+    return track.CoverArtPath
+        ? {
+            coverArtPath: track.CoverArtPath,
+            coverArtSmall: track.CoverArtSmall,
+            coverArtMedium: track.CoverArtMedium,
+            coverArtLarge: track.CoverArtLarge,
+        }
+        : undefined;
+}
+
+/**
+ * What became of the attempt.
+ *
+ * `chunk-failed` is separate from `not-in-library` because
+ * `loadTrackDetails` has already told the user about it — a caller that
+ * treated the two alike would report a missing track over the top of a
+ * notification saying the dialog itself could not be fetched.
+ */
+export type TrackDetailsOutcome = 'shown' | 'not-in-library' | 'chunk-failed';
+
+/**
+ * Show the details dialog for the library track at `filePath`.
+ *
+ * @param dialog A getter, not the element: `@query` resolves an
+ *               un-upgraded `<track-details>` before the chunk lands,
+ *               and only the read *after* `loadTrackDetails` is
+ *               guaranteed to have `show()` on it.
+ * @param retry  Re-runs the action that wanted the dialog, offered to
+ *               the user if the chunk could not be fetched.
+ */
+export async function showTrackDetailsForPath(
+    dialog: () => TrackDetails | undefined,
+    filePath: string,
+    retry: () => void,
+): Promise<TrackDetailsOutcome> {
+    const tracks = await libraryStore.getTracks();
+    const track = tracksByFilePath(tracks).get(filePath);
+
+    if (!track) return 'not-in-library';
+
+    const ready = await loadTrackDetails(retry);
+
+    if (!ready) return 'chunk-failed';
+
+    dialog()?.show(track, coverArtOf(track));
+
+    return 'shown';
+}