feat(library): answer album completeness for a screenful in one query

A card grid has to know how much of an album is here — an album held 2
tracks of 10 wearing the same green tick as one held whole is the
complaint the badge-accuracy work was filed about — and
`GetAlbumCompleteness` is one query per album, which is fifty round
trips for a grid of fifty.

`GetAlbumsCompleteness` is the same question over a slice. It is two
grouping levels rather than the single-album form's correlated
subqueries, because a correlated subquery in the FROM clause is not
something SQLite will reliably do, and because the slice may only be
spelled once or sqlc expands it twice with independently numbered
placeholders.

An album with no files is absent from the result rather than zeroed:
"I have none of this" and "I have no idea" are the third state `Known`
exists to keep apart.

The test that matters is that the two spellings never disagree — they
are genuinely different SQL, so the risk is a drift in meaning (a
disc's total counted once per file, a duplicate counted twice) rather
than a typo.

frontend/bindings/yellowjacket/backend/library/library.ts

@@ -98,6 +98,26 @@ export function GetAlbumsByArtist(artist: string, libraryID: number): $Cancellab
     return $Call.ByID(1456840721, artist, libraryID);
 }
 
+/**
+ * GetAlbumsCompleteness answers the same question for a screenful of
+ * albums in one query, keyed by album id.
+ * 
+ * A card grid asks this about every card that has a local album behind
+ * it, and one query per card is how a grid of fifty albums becomes
+ * fifty round trips. The answer matters there for the reason it
+ * matters on the album page: an album held 9 tracks of 12 has to show
+ * the count, and a bare tick saying "in your library" is the complaint
+ * this whole rule came from.
+ * 
+ * An album with no row in the result is one with no files, and it is
+ * absent rather than zeroed — "I have none of this" and "I have no
+ * idea" are the same third state `Known` exists to keep apart, and a
+ * caller reading a missing key gets nothing rather than a confident 0.
+ */
+export function GetAlbumsCompleteness(albumIDs: number[] | null): $CancellablePromise<{ [_ in `${number}`]?: $models.AlbumCompleteness } | null> {
+    return $Call.ByID(531636827, albumIDs);
+}
+
 /**
  * GetAllLibrariesWithTrackCounts lists the libraries and their sizes.
  */