feat: add PiP, fullscreen, and playbackRate helpers to playback module

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/transport/playback.ts

@@ -96,6 +96,58 @@ export function adjustShuttle(dir: 1 | -1, shuttleRate: number): number {
   return nextRate;
 }
 
+export function togglePiP(): void {
+  if (document.pictureInPictureElement) {
+    document.exitPictureInPicture().catch((e) => {
+      console.error('Exit PiP failed:', e);
+    });
+  } else {
+    const videoEl = getVideo();
+    if (videoEl && document.pictureInPictureEnabled) {
+      videoEl.requestPictureInPicture().catch((e) => {
+        console.error('PiP request failed:', e);
+      });
+    }
+  }
+}
+
+export function isPiPActive(): boolean {
+  return !!document.pictureInPictureElement;
+}
+
+export function toggleFullscreen(): void {
+  if (document.fullscreenElement) {
+    document.exitFullscreen().catch((e) => {
+      console.error('Exit fullscreen failed:', e);
+    });
+  } else {
+    const videoEl = getVideo();
+    if (!videoEl) return;
+    if (videoEl.requestFullscreen) {
+      videoEl.requestFullscreen().catch((e) => {
+        console.error('Fullscreen request failed:', e);
+      });
+    } else if ((videoEl as HTMLVideoElement & { webkitEnterFullscreen?: () => void }).webkitEnterFullscreen) {
+      (videoEl as HTMLVideoElement & { webkitEnterFullscreen: () => void }).webkitEnterFullscreen();
+    }
+  }
+}
+
+export function isFullscreenActive(): boolean {
+  return !!document.fullscreenElement;
+}
+
+export function setPlaybackRate(rate: number): void {
+  const videoEl = getVideo();
+  if (videoEl) {
+    videoEl.playbackRate = rate;
+  }
+}
+
+export function getPlaybackRate(): number {
+  return getVideo()?.playbackRate ?? 1;
+}
+
 export type TransportKeyAction =
   | 'play-pause'
   | 'frame-back'