refactor(decouple): move coerceOpenArtistRefs to lib/api (off artist feature)

First step of decoupling the audio core from feature imports. coerceOpenArtist
Refs is a pure Subsonic-response normalizer (one-object-vs-array quirk) that was
mis-membered in features/artist but consumed by the audio core (songToTrack,
trackArtistRefs) and others. Relocate it beside its SubsonicOpenArtistRef type in
lib/api/; drop the artist-barrel re-export; repoint the 4 barrel consumers.

Removes the @/features/artist runtime edge from the audio core (utils/playback)
entirely. tsc 0, lint 0/0, suite 319/2353 green.

(composerBrowseSessionStore's ALL_SENTINEL import from @/features/artist remains
— that's a non-audio global browse store, separate from this decouple.)

src/features/album/utils/deriveAlbumHeaderArtistRefs.ts

@@ -1,5 +1,5 @@
 import type { SubsonicAlbum, SubsonicOpenArtistRef, SubsonicSong } from '@/lib/api/subsonicTypes';
-import { coerceOpenArtistRefs } from '@/features/artist';
+import { coerceOpenArtistRefs } from '@/lib/api/openArtistRefs';
 
 function nonEmpty(refs: SubsonicOpenArtistRef[]): refs is SubsonicOpenArtistRef[] {
   return refs.length > 0;

src/features/artist/index.ts

@@ -27,7 +27,6 @@ export * from './store/artistAlbumYearSortStore';
 export * from './store/artistBrowseSessionStore';
 export * from './store/artistLayoutStore';
 export * from './utils/artistsHelpers';
-export * from './utils/openArtistRefs';
 export * from './utils/runArtistDetailActions';
 export * from './utils/runArtistDetailPlay';
 export * from './utils/sortArtistAlbums';

src/features/artist/utils/openArtistRefs.test.ts

@@ -1,19 +0,0 @@
-import { describe, expect, it } from 'vitest';
-import { coerceOpenArtistRefs } from '@/features/artist/utils/openArtistRefs';
-
-describe('coerceOpenArtistRefs', () => {
-  it('returns an empty array for nullish input', () => {
-    expect(coerceOpenArtistRefs(undefined)).toEqual([]);
-    expect(coerceOpenArtistRefs(null)).toEqual([]);
-  });
-
-  it('passes through arrays', () => {
-    const refs = [{ id: 'a1', name: 'One' }, { id: 'a2', name: 'Two' }];
-    expect(coerceOpenArtistRefs(refs)).toBe(refs);
-  });
-
-  it('wraps a single ref object from Subsonic JSON', () => {
-    const ref = { id: 'a1', name: 'Solo' };
-    expect(coerceOpenArtistRefs(ref)).toEqual([ref]);
-  });
-});

src/features/artist/utils/openArtistRefs.ts

@@ -1,11 +0,0 @@
-import type { SubsonicOpenArtistRef } from '@/lib/api/subsonicTypes';
-
-/** Subsonic JSON may return one ref object instead of a one-element array. */
-export function coerceOpenArtistRefs(
-  refs: SubsonicOpenArtistRef[] | SubsonicOpenArtistRef | undefined | null,
-): SubsonicOpenArtistRef[] {
-  if (refs == null) return [];
-  if (Array.isArray(refs)) return refs;
-  if (typeof refs === 'object') return [refs];
-  return [];
-}