fix(player): return from background audio onto the episode it advanced to

An episode that ends while backgrounded in audio-only mode advances in the
backend, but player_exit_background_audio returned only a position, so the
video page reloaded the episode it was mounted with -- the previous one, at
the new episode's timestamp.

The command now returns BackgroundAudioResume { itemId, positionSeconds }.
planHandoffReturn yields "other-item" when the id differs from the mounted
one, and the player page navigates to that episode with resumeAt=<seconds>,
marking the outgoing episode watched and suppressing its stale stop report.

TRACES: UR-040, UR-023 | DR-296 | UT-265, UT-266

src/lib/api/bindings.ts

@@ -66,9 +66,14 @@ async playerEnterBackgroundAudio(item: PlayItemRequest, positionSeconds: number)
     return await TAURI_INVOKE("player_enter_background_audio", { item, positionSeconds });
 },
 /**
- * TRACES: UR-040 | DR-052 | UT-061, IT-013
+ * Returns the item the native player is on and its absolute position. The
+ * item matters: an episode that ended while backgrounded has already advanced
+ * in the backend, so reloading the video the webview was mounted with would
+ * bring back the previous episode. (DR-296)
+ * 
+ * TRACES: UR-040, UR-023 | DR-052, DR-296 | UT-061, IT-013
  */
-async playerExitBackgroundAudio() : Promise<number> {
+async playerExitBackgroundAudio() : Promise<BackgroundAudioResume> {
     return await TAURI_INVOKE("player_exit_background_audio");
 },
 /**
@@ -2190,6 +2195,22 @@ export type BackgroundAction =
  * Stop making sound. The user did not ask for background playback.
  */
 "pause"
+/**
+ * Where playback stands when a background-audio handoff returns to the
+ * foreground. See [`PlayerController::background_audio_resume`].
+ * 
+ * TRACES: UR-040, UR-023 | DR-296
+ */
+export type BackgroundAudioResume = { 
+/**
+ * Item the native audio player is on — `None` if the queue emptied (e.g.
+ * the sleep timer stopped playback while backgrounded).
+ */
+itemId: string | null; 
+/**
+ * Absolute position in that item, in seconds.
+ */
+positionSeconds: number }
 /**
  * Smart caching configuration
  */