fix(albums): order each artist's albums by title when sorting by artist (#1115)

* fix(albums): order each artist's albums by title when sorting by artist

Browsing albums by artist left the albums within each artist in an
undefined order. The local-index sort only emitted the artist key; it
now appends album title as a secondary key (and artist as the tiebreak
for the by-name sort), matching the network path's per-page ordering.

* docs(changelog): note album sort-within-artist fix (#1115)

src/utils/library/albumBrowseSort.test.ts

@@ -0,0 +1,51 @@
+import { describe, expect, it } from 'vitest';
+import type { SubsonicAlbum } from '../../api/subsonicTypes';
+import { albumSortClauses, sortSubsonicAlbums } from './albumBrowseSort';
+
+const album = (artist: string, name: string): SubsonicAlbum =>
+  ({ id: `${artist}-${name}`, artist, name }) as SubsonicAlbum;
+
+describe('albumSortClauses', () => {
+  it('sorts by artist then album name', () => {
+    expect(albumSortClauses('alphabeticalByArtist')).toEqual([
+      { field: 'artist', dir: 'asc' },
+      { field: 'name', dir: 'asc' },
+    ]);
+  });
+
+  it('sorts by album name then artist', () => {
+    expect(albumSortClauses('alphabeticalByName')).toEqual([
+      { field: 'name', dir: 'asc' },
+      { field: 'artist', dir: 'asc' },
+    ]);
+  });
+});
+
+describe('sortSubsonicAlbums', () => {
+  it('orders each artist group by album name when sorting by artist', () => {
+    const input = [
+      album('Rammstein', 'Sehnsucht'),
+      album('Duran Duran', 'Rio'),
+      album('Rammstein', 'Mutter'),
+      album('Duran Duran', 'DD'),
+      album('Duran Duran', 'The Wedding Album'),
+    ];
+    const ordered = sortSubsonicAlbums(input, 'alphabeticalByArtist').map(a => `${a.artist} - ${a.name}`);
+    expect(ordered).toEqual([
+      'Duran Duran - DD',
+      'Duran Duran - Rio',
+      'Duran Duran - The Wedding Album',
+      'Rammstein - Mutter',
+      'Rammstein - Sehnsucht',
+    ]);
+  });
+
+  it('breaks album-name ties by artist when sorting by name', () => {
+    const input = [
+      album('Zebra', 'Greatest Hits'),
+      album('Alpha', 'Greatest Hits'),
+    ];
+    const ordered = sortSubsonicAlbums(input, 'alphabeticalByName').map(a => a.artist);
+    expect(ordered).toEqual(['Alpha', 'Zebra']);
+  });
+});

src/utils/library/albumBrowseSort.ts

@@ -4,10 +4,19 @@ import type { LibrarySortClause } from '../../api/library';
 export type AlbumBrowseSort = 'alphabeticalByName' | 'alphabeticalByArtist';
 
 export function albumSortClauses(sort: AlbumBrowseSort): LibrarySortClause[] {
+  // Always append a secondary key so albums sharing the primary key keep a
+  // stable order — by artist groups each artist's albums by title (rather than
+  // an undefined order within the artist), mirroring `sortSubsonicAlbums`.
   if (sort === 'alphabeticalByArtist') {
-    return [{ field: 'artist', dir: 'asc' }];
+    return [
+      { field: 'artist', dir: 'asc' },
+      { field: 'name', dir: 'asc' },
+    ];
   }
-  return [{ field: 'name', dir: 'asc' }];
+  return [
+    { field: 'name', dir: 'asc' },
+    { field: 'artist', dir: 'asc' },
+  ];
 }
 
 export function sortSubsonicAlbums(albums: SubsonicAlbum[], sort: AlbumBrowseSort): SubsonicAlbum[] {