feat(player): guard against audio playback on secondary device

frontend/angular/src/app/features/player/player-shell.component.spec.ts

@@ -350,4 +350,29 @@ describe('PlayerShellComponent gameplay wiring', () => {
 
     component.ngOnDestroy();
   });
+
+  it('installs secondary-device audio guard while player shell is mounted', async () => {
+    const originalPlay = vi.fn().mockRejectedValue(new Error('original play'));
+    const mediaPrototype = { play: originalPlay };
+
+    vi.stubGlobal('window', {
+      location: { hash: '', search: '' },
+      history: { state: null, replaceState: vi.fn() },
+      localStorage: { getItem: vi.fn().mockReturnValue('en'), setItem: vi.fn(), removeItem: vi.fn() },
+      sessionStorage: { getItem: vi.fn().mockReturnValue(null), setItem: vi.fn(), removeItem: vi.fn() },
+      HTMLMediaElement: { prototype: mediaPrototype },
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+    });
+    vi.stubGlobal('navigator', { language: 'en-US', onLine: true });
+
+    const component = new PlayerShellComponent();
+    component.ngOnInit();
+
+    await expect(mediaPrototype.play()).resolves.toBeUndefined();
+
+    component.ngOnDestroy();
+
+    await expect(mediaPrototype.play()).rejects.toThrow('original play');
+  });
 });

frontend/angular/src/app/features/player/player-shell.component.ts

@@ -113,6 +113,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
   private reconnectTimer: ReturnType<typeof setTimeout> | null = null;
   private stateSyncTimer: ReturnType<typeof setTimeout> | null = null;
   private unsubscribeLocale: (() => void) | null = null;
+  private restoreAudioGuard: (() => void) | null = null;
 
   constructor() {
     if (typeof navigator !== 'undefined' && !navigator.onLine) {
@@ -129,6 +130,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     this.unsubscribeLocale = subscribeToLocaleChanges((locale) => {
       this.locale = locale;
     });
+    this.installSecondaryDeviceAudioGuard();
 
     const hashRoute = window.location.hash.replace(/^#\/?/, '');
     const match = hashRoute.match(/^player(?:\/[^/]+)?(?:\/([^/?#]+))?/i);
@@ -158,6 +160,8 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     this.clearStateSyncTimer();
     this.unsubscribeLocale?.();
     this.unsubscribeLocale = null;
+    this.restoreAudioGuard?.();
+    this.restoreAudioGuard = null;
   }
 
   private readonly handleOnline = (): void => {
@@ -185,6 +189,25 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     }
   }
 
+  private installSecondaryDeviceAudioGuard(): void {
+    if (!this.clientHasNoAudioOutput || typeof window === 'undefined') {
+      return;
+    }
+
+    const mediaPrototype = (window as Window & { HTMLMediaElement?: { prototype?: { play?: () => Promise<void> } } }).HTMLMediaElement
+      ?.prototype;
+
+    if (!mediaPrototype || typeof mediaPrototype.play !== 'function') {
+      return;
+    }
+
+    const originalPlay = mediaPrototype.play;
+    mediaPrototype.play = () => Promise.resolve();
+    this.restoreAudioGuard = () => {
+      mediaPrototype.play = originalPlay;
+    };
+  }
+
   private scheduleStateSync(): void {
     this.clearStateSyncTimer();