fix(dashboard): read M3U favorites after queued favorite writes

getM3uFavoriteChannels could query SQLite before a just-toggled favorite
was written: updateFavorites is serialized per playlist and can land late,
while the dashboard reads as soon as the store changes and never reloads
because playlistFavoritesReloadKey is unchanged. Await the playlist's write
queue tail (which never rejects) before reading.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.changes/dashboard-fresh-m3u-favorite.md

@@ -0,0 +1,8 @@
+---
+type: fix
+area: dashboard
+---
+
+An M3U channel added to favorites right before opening the dashboard now
+appears in the favorites rail immediately, instead of only after the next
+reload.

libs/services/src/lib/playlists.service.spec.ts

@@ -345,6 +345,49 @@ describe('PlaylistsService', () => {
         expect(electron.dbGetAppPlaylists).not.toHaveBeenCalled();
     });
 
+    it('reads resolved M3U favorites only after a queued favorites write lands', async () => {
+        let storedFavorites: string[] = [];
+        let releaseWrite!: () => void;
+        const writeGate = new Promise<void>((resolve) => {
+            releaseWrite = resolve;
+        });
+        const electron = {
+            dbGetAppPlaylist: jest.fn(async () => {
+                await writeGate;
+                return { _id: 'playlist-1', favorites: storedFavorites };
+            }),
+            dbGetAppPlaylistFavoriteChannels: jest.fn(async () =>
+                storedFavorites.map((id) => ({ id }))
+            ),
+            dbGetAppPlaylists: jest.fn(async () => []),
+            dbGetAppState: jest.fn(async (key: string) =>
+                key === SQLITE_PLAYLIST_MIGRATION_FLAG ||
+                key === STALKER_PLAYLIST_METADATA_MIGRATION_FLAG
+                    ? '1'
+                    : null
+            ),
+            dbSetAppState: jest.fn(),
+            dbUpsertAppPlaylist: jest.fn(async (playlist: Playlist) => {
+                storedFavorites = playlist.favorites as string[];
+            }),
+            dbUpsertAppPlaylists: jest.fn(),
+        };
+        testWindow.electron = electron;
+
+        const service = createService();
+        const write = firstValueFrom(
+            service.updateFavorites('playlist-1', ['channel-1'])
+        );
+        const read = firstValueFrom(
+            service.getM3uFavoriteChannels('playlist-1')
+        );
+        await new Promise((resolve) => setTimeout(resolve));
+        releaseWrite();
+
+        await write;
+        await expect(read).resolves.toEqual([{ id: 'channel-1' }]);
+    });
+
     it('falls back from resolved M3U favorites when SQLite playlist migration is incomplete', async () => {
         const electron = {
             dbGetAppPlaylist: jest.fn(),

libs/services/src/lib/playlists.service.ts

@@ -1092,6 +1092,9 @@ export class PlaylistsService {
 
         return from(
             (async () => {
+                // A favorite toggled just before this read may still be queued;
+                // the queue tail never rejects.
+                await this.playlistWriteQueues.get(playlistId);
                 const alreadyMigrated = await electron.dbGetAppState(
                     SQLITE_PLAYLIST_MIGRATION_FLAG
                 );