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

backend/explore/prune_test.go

@@ -5,7 +5,6 @@ import (
 	"testing"
 
 	"yellowjacket/backend/database"
-	"yellowjacket/backend/database/sql/sqlcgen"
 )
 
 // TestPruneStaleLocalCrossReferences verifies that an explore_index row
@@ -21,10 +20,17 @@ func TestPruneStaleLocalCrossReferences(t *testing.T) {
 	db := database.NewTestDB(t)
 	si := NewSearchIndex(db, nil, nil, slog.Default())
 
-	// A library artist that still exists.
-	artist, err := db.Queries.UpsertArtist(t.Context(), "Still Owned")
+	// A library artist that still exists - which now means one with a
+	// file behind it.  An artist row on its own is not ownership; that
+	// was the whole bug.
+	database.InsertTestTrack(t, db, database.TestTrack{
+		FilePath: "/music/still-owned.mp3",
+		Artist:   "Still Owned",
+	})
+
+	artist, err := db.Queries.GetArtistByName(t.Context(), "Still Owned")
 	if err != nil {
-		t.Fatalf("upsert artist: %v", err)
+		t.Fatalf("read seeded artist: %v", err)
 	}
 
 	// Two explore_index artist rows: one pointing at the still-existing
@@ -33,19 +39,15 @@ func TestPruneStaleLocalCrossReferences(t *testing.T) {
 	seedArtist := func(mbid, title string, localID int64) {
 		t.Helper()
 
-		if _, err := db.ExecContext(
-			upsertIndexSQL,
-			"artist", mbid, title, title, mbid, "",
-			0, 0,
-			0, "", "",
-			"", "", "",
-			"", "", "", "",
-			1, 0,
-			localID, 0, 0,
-			0,
-		); err != nil {
-			t.Fatalf("seed explore_index row for %q: %v", mbid, err)
-		}
+		seedIndexResult(t, db, SearchIndexResult{
+			EntityType:    EntityArtist,
+			MBID:          testMBID(mbid),
+			Title:         title,
+			ArtistName:    title,
+			ArtistMBID:    testMBID(mbid),
+			InLibrary:     true,
+			LocalArtistID: localID,
+		})
 	}
 
 	seedArtist("still-owned-mbid", "Still Owned", artist.ID)
@@ -53,7 +55,7 @@ func TestPruneStaleLocalCrossReferences(t *testing.T) {
 
 	si.pruneStaleLocalCrossReferences()
 
-	stillOwned := si.LookupArtistByMBID("still-owned-mbid")
+	stillOwned := si.LookupArtistByMBID(testMBID("still-owned-mbid"))
 	if stillOwned == nil {
 		t.Fatal("expected still-owned artist row to survive pruning")
 	}
@@ -67,7 +69,7 @@ func TestPruneStaleLocalCrossReferences(t *testing.T) {
 		)
 	}
 
-	removed := si.LookupArtistByMBID("removed-mbid")
+	removed := si.LookupArtistByMBID(testMBID("removed-mbid"))
 	if removed == nil {
 		t.Fatal("expected removed-artist row to still exist (only cross-references cleared)")
 	}
@@ -90,51 +92,18 @@ func TestUnenrichedLibraryArtistMBIDs_OrdersByOwnedTrackCount(t *testing.T) {
 
 	db := database.NewTestDB(t)
 	si := NewSearchIndex(db, nil, nil, slog.Default())
-	q := db.Queries
-	ctx := t.Context()
 
 	seedArtistWithTracks := func(name, mbid string, trackCount int) {
 		t.Helper()
 
-		artist, err := q.UpsertArtist(ctx, name)
-		if err != nil {
-			t.Fatalf("upsert artist %q: %v", name, err)
-		}
-
-		_, err = db.ExecContext("UPDATE artists SET mbid = ? WHERE id = ?", mbid, artist.ID)
-		if err != nil {
-			t.Fatalf("set mbid for %q: %v", name, err)
-		}
-
-		ac, err := q.UpsertArtistCredit(ctx, name)
-		if err != nil {
-			t.Fatalf("upsert artist credit %q: %v", name, err)
-		}
-
-		if _, err := q.CreateArtistCreditArtist(ctx, sqlcgen.CreateArtistCreditArtistParams{
-			ArtistID: artist.ID,
-			CreditID: ac.ID,
-		}); err != nil {
-			t.Fatalf("link artist credit artist %q: %v", name, err)
-		}
-
 		for i := range trackCount {
-			rec, err := q.CreateRecordingFull(ctx, sqlcgen.CreateRecordingFullParams{
-				Name:           name,
-				ArtistCreditID: ac.ID,
+			database.InsertTestTrack(t, db, database.TestTrack{
+				FilePath:   name + "/" + string(rune('a'+i)) + ".mp3",
+				Title:      name,
+				Artist:     name,
+				ArtistMBID: mbid,
+				LengthMs:   180000,
 			})
-			if err != nil {
-				t.Fatalf("create recording for %q: %v", name, err)
-			}
-
-			if _, err := q.CreateAudioFile(ctx, sqlcgen.CreateAudioFileParams{
-				FilePath:           name + "/" + string(rune('a'+i)) + ".mp3",
-				LengthMilliseconds: 180000,
-				RecordingID:        rec.ID,
-				Basename:           string(rune('a'+i)) + ".mp3",
-			}); err != nil {
-				t.Fatalf("create audio file for %q: %v", name, err)
-			}
 		}
 	}