fix(overlay): force packed float audio for macOS timing review preview

- Pass --audio-format=float to the preview mpv on darwin so coreaudio accepts Opus output on Bluetooth devices like AirPods instead of falling back to avfoundation
- Fixes the stuttering preview cursor that jumped to the end partway through the selection
- Thread the platform into buildMediaTimingPreviewArgs and add a test covering darwin vs linux args

changes/timing-review-macos-cursor.md

@@ -0,0 +1,4 @@
+type: fixed
+area: overlay
+
+- On macOS with Bluetooth headphones such as AirPods, the timing review preview cursor now moves smoothly across the selection instead of stuttering and jumping to the end partway through. This affected Opus audio, including Jellyfin streams.

src/core/services/media-timing-preview.test.ts

@@ -39,6 +39,22 @@ describe('buildMediaTimingPreviewArgs', () => {
     );
   });
 
+  test('keeps macOS previews on coreaudio with packed float output', () => {
+    const options = { mediaPath: '/tmp/window.mkv' };
+
+    assert.ok(
+      buildMediaTimingPreviewArgs('/tmp/review.sock', options, 'darwin').includes(
+        '--audio-format=float',
+      ),
+    );
+    assert.equal(
+      buildMediaTimingPreviewArgs('/tmp/review.sock', options, 'linux').some((arg) =>
+        arg.startsWith('--audio-format='),
+      ),
+      false,
+    );
+  });
+
   test('separates an option-like media path without adding optional audio arguments', () => {
     const args = buildMediaTimingPreviewArgs('/tmp/review.sock', {
       mediaPath: '--fullscreen',

src/core/services/media-timing-preview.ts

@@ -44,6 +44,7 @@ interface MediaTimingPreviewDeps {
 export function buildMediaTimingPreviewArgs(
   socketPath: string,
   options: MediaTimingPreviewStartOptions,
+  platform: NodeJS.Platform = process.platform,
 ): string[] {
   const args = [
     '--no-config',
@@ -66,6 +67,12 @@ export function buildMediaTimingPreviewArgs(
   if (options.absoluteTimestamps) {
     args.push('--rebase-start-time=no');
   }
+  if (platform === 'darwin') {
+    // coreaudio can reject planar float (what Opus decodes to) on Bluetooth outputs such as
+    // AirPods, and mpv then falls back to avfoundation. Its 2 s device buffer makes time-pos
+    // updates sparse and ends the clip well before the audio does, so the preview cursor jumps.
+    args.push('--audio-format=float');
+  }
   args.push('--', options.mediaPath);
   return args;
 }
@@ -170,7 +177,7 @@ export class MediaTimingPreviewSession {
     this.startupError = null;
     const child = this.deps.spawnProcess(
       command,
-      buildMediaTimingPreviewArgs(socketPath, { ...options, mediaPath }),
+      buildMediaTimingPreviewArgs(socketPath, { ...options, mediaPath }, this.deps.platform),
     );
     this.process = child;
     child.once('error', (error) => {