fix(android): instant cold-start resume + play button icon flicker

WebBridge: skip setMediaItems/prepare when the track is already buffered
from the cold-start pre-warm, so resuming the last song is instant (~0s)
instead of re-buffering from scratch (~10s).

Player: show pause icon during buffering (isPlaying=false, isBuffering=true)
so the button doesn't flash back to "play" between tracks. Also optimistically
set _nativePlaying=true and call setPlayIcon immediately on playCurrent so the
icon updates before the native callback round-trip.

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

android/app/src/main/kotlin/com/novasonic/app/WebBridge.kt

@@ -28,11 +28,20 @@ class WebBridge(private val controllerProvider: () -> MediaController?) {
         runOnMain {
             val ctrl = controllerProvider() ?: return@runOnMain
             val idx = startIndex.coerceAtLeast(0)
+            // If ExoPlayer already has this exact single track buffered from the cold-start
+            // pre-warm, skip setMediaItems+prepare so we don't throw away the buffered data.
+            // Just call play() — this makes the "resume last track" instant instead of ~10s.
+            val alreadyReady = items.size == 1 &&
+                ctrl.mediaItemCount == 1 &&
+                ctrl.currentMediaItem?.mediaId == items[0].mediaId &&
+                ctrl.playbackState != Player.STATE_IDLE
+            if (!alreadyReady) {
                 ctrl.setMediaItems(items, idx, 0L)
                 // Pre-warm artwork before prepare()/play() so the notification bitmap
                 // cache is populated before Media3 renders the first notification.
                 MusicService.instance?.publicWarmArtwork(idx)
                 ctrl.prepare()
+            }
             if (autoPlay) ctrl.play()
         }
     }

src/player/player.js

@@ -189,9 +189,12 @@ window.NSPlayer = {
       _nativePlaying = state.isPlaying;
       if (!state.isPlaying && !state.isBuffering) _cancelScrobble();
       if (state.isPlaying && S.previewCurrent) stopPreview(false);
+      // Show pause icon while buffering (isPlaying=false but isBuffering=true) so the
+      // button doesn't flash "play" during the brief re-buffer between tracks.
+      const showPlaying = state.isPlaying || state.isBuffering;
       if (state.isPlaying !== prev) {
-        setPlayIcon(state.isPlaying);
-        document.getElementById('player-art')?.classList.toggle('spinning', state.isPlaying);
+        setPlayIcon(showPlaying);
+        document.getElementById('player-art')?.classList.toggle('spinning', showPlaying);
         if (navigator.mediaSession)
           navigator.mediaSession.playbackState = state.isPlaying ? 'playing' : 'paused';
       }
@@ -374,8 +377,10 @@ export function playCurrent() {
 
   if (HAS_BRIDGE) {
     S._trackChanging = true;
+    _nativePlaying = true;
     _resetProgressUI();
     updatePlayerUI(s, true);
+    setPlayIcon(true);
     onNpSongChange(s.id);
     renderQueue();
     try { window.NSBridge.setQueue(_nativeSingle(s), 0, true); } catch(_) {}