fix(audio): don't restart playback on device change when engine is paused

Defence-in-depth for #1094: the device-changed/-reset handlers restarted
playback based on the UI `isPlaying` flag alone, which can be stale or
desynced at the moment of a device change. Gate the restart on the
engine-paused flag as well (`isPlaying && !getIsAudioPaused()`), so a
paused engine never auto-restarts regardless of how `isPlaying` got set;
when paused it just resets for the cold path. Adds a regression test.

(cherry picked from commit 588dd8c48d)

src/hooks/tauriBridge/useAudioDeviceBridge.test.ts

@@ -18,6 +18,7 @@ import { makeTrack } from '@/test/helpers/factories';
 import { usePlayerStore } from '@/store/playerStore';
 import { useAuthStore } from '@/store/authStore';
 import { getSeekFallbackVisualTarget, setSeekFallbackVisualTarget } from '@/store/seekFallbackState';
+import { setIsAudioPaused } from '@/store/engineState';
 import { useAudioDeviceBridge } from './useAudioDeviceBridge';
 
 const track = makeTrack({ id: 't1', duration: 300 });
@@ -29,6 +30,8 @@ function mountBridge() {
 beforeEach(() => {
   resetAllStores();
   setSeekFallbackVisualTarget(null);
+  // Module-level engine flag isn't covered by resetAllStores — reset explicitly.
+  setIsAudioPaused(false);
   // Default: a track is playing.
   usePlayerStore.setState({ currentTrack: track, isPlaying: true });
 });
@@ -92,6 +95,19 @@ describe('audio:device-changed', () => {
 
     expect(playTrack).not.toHaveBeenCalled();
   });
+
+  it('does not restart when the engine is paused even if isPlaying is stale-true (#1094)', () => {
+    const playTrack = vi.fn();
+    const resetAudioPause = vi.fn();
+    usePlayerStore.setState({ playTrack, resetAudioPause, isPlaying: true } as never);
+    setIsAudioPaused(true);
+    mountBridge();
+
+    emitTauriEvent('audio:device-changed', 45.0);
+
+    expect(playTrack).not.toHaveBeenCalled();
+    expect(resetAudioPause).toHaveBeenCalled();
+  });
 });
 
 // ─── audio:device-reset ─────────────────────────────────────────────────────

src/hooks/tauriBridge/useAudioDeviceBridge.ts

@@ -3,6 +3,7 @@ import { listen } from '@tauri-apps/api/event';
 import { usePlayerStore } from '../../store/playerStore';
 import { useAuthStore } from '../../store/authStore';
 import { setSeekFallbackVisualTarget } from '../../store/seekFallbackState';
+import { getIsAudioPaused } from '../../store/engineState';
 
 /** Audio output device lifecycle: device switches (Bluetooth headphones, USB
  * DAC, …) and pinned-device-unplugged fallbacks emitted by the Rust
@@ -23,7 +24,10 @@ export function useAudioDeviceBridge() {
       const resumeAt = typeof event.payload === 'number' ? event.payload : 0;
       const { currentTrack, isPlaying, playTrack, resetAudioPause } = usePlayerStore.getState();
       if (!currentTrack) return;
-      if (isPlaying) {
+      // Only restart playback when transport is *provably* active. `isPlaying`
+      // alone can be stale/desynced on a device change (#1094); the engine-paused
+      // flag is the source of truth — if paused, just reset for the cold path.
+      if (isPlaying && !getIsAudioPaused()) {
         if (resumeAt > 0.5 && currentTrack.duration > 0) {
           setSeekFallbackVisualTarget({
             trackId: currentTrack.id,
@@ -55,7 +59,10 @@ export function useAudioDeviceBridge() {
       const resumeAt = typeof event.payload === 'number' ? event.payload : 0;
       const { currentTrack, isPlaying, playTrack, resetAudioPause } = usePlayerStore.getState();
       if (!currentTrack) return;
-      if (isPlaying) {
+      // Only restart playback when transport is *provably* active. `isPlaying`
+      // alone can be stale/desynced on a device change (#1094); the engine-paused
+      // flag is the source of truth — if paused, just reset for the cold path.
+      if (isPlaying && !getIsAudioPaused()) {
         if (resumeAt > 0.5 && currentTrack.duration > 0) {
           setSeekFallbackVisualTarget({
             trackId: currentTrack.id,