test(m3): retarget collapsed barrel mocks to deep submodules

The move tool rewrote single-module mocks (e.g. vi.mock('@/utils/orbitBulkGuard'))
into feature-BARREL mocks (vi.mock('@/features/orbit', ...)). A partial barrel
factory shadows every other barrel export to undefined — and src/test/helpers/
storeReset.ts reads useOrbitStore.getState() at module load, so 6 test files
(playerStore.misc/events/queue/playbackActions, ContextMenu, QueuePanel) crashed
at collection (0 tests run, mis-read as flaky teardown). Retarget each collapsed
mock to its deep submodule so the barrel re-exports the stub while siblings
(useOrbitStore, offlineActionPolicy, usePlaylistStore) stay real.

src/features/offline/utils/pinnedOfflineSync.test.ts

@@ -29,7 +29,7 @@ vi.mock('@/utils/network/activeServerReachability', () => ({
   onActiveServerBecameReachable: () => () => {},
 }));
 
-vi.mock('@/features/playlist', () => ({
+vi.mock('@/features/playlist/api/subsonicPlaylists', () => ({
   getPlaylistForServer: (serverId: string, id: string) => getPlaylistMock(serverId, id),
 }));