fix: NP overlay shows stale song on Android auto-advance

openNowPlaying() was blindly trusting the MediaController snapshot index,
which can lag one track behind ExoPlayer on auto-advance. This overwrote
the already-correct S.qIdx that onTrackChanged had just set, causing the
NP overlay to render the previous song while the mini-player showed the
right one. Now only accept the snapshot index when the song ID at that
position matches — stale snapshots are silently ignored.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/nowplaying.js

@@ -8,13 +8,19 @@ import { openPlModal, showSongInfo } from './ui.js';
 
 // ─── NOW PLAYING OVERLAY ───
 export function openNowPlaying() {
-  // On Android, onTrackChanged is async — query native for the current index
-  // before rendering so we never show the previous song for a flash.
+  // On Android, verify the snapshot index before using it — the MediaController
+  // snapshot can lag behind ExoPlayer by one track on auto-advance.  Only accept
+  // it when the song ID at that position matches (i.e. snapshot is not stale).
   if (typeof window.NSBridge !== 'undefined') {
     try {
       const state = JSON.parse(window.NSBridge.getState() || '{}');
-      if (typeof state.currentIndex === 'number' && state.currentIndex >= 0 && state.currentIndex < S.queue.length)
-        S.qIdx = state.currentIndex;
+      const snapIdx = state.currentIndex;
+      const snapId  = state.currentId || '';
+      if (typeof snapIdx === 'number' && snapIdx >= 0 && snapIdx < S.queue.length) {
+        const expected = S.queue[snapIdx];
+        if (!snapId || !expected?.id || String(snapId) === String(expected.id))
+          S.qIdx = snapIdx;
+      }
     } catch {}
   }
   S.npOpen = true;