fix: support multiple onTimeUpdate callbacks in VideoManager

Previously onTimeCallback was a single nullable function pointer, so
registerEvents()'s store.setVideoTime callback was overwritten by
goToScene()'s checkQTE callback, causing videoTime to stay at 0.
Changed to a Set to support multiple concurrent listeners.

engine/core/VideoManager.ts

@@ -7,7 +7,7 @@ export class VideoManager {
   private activeSlot: 'A' | 'B' = 'A'
   private crossFadeMs = 300
   private onEndCallback: VideoEndCallback | null = null
-  private onTimeCallback: TimeUpdateCallback | null = null
+  private onTimeCallbacks: Set<TimeUpdateCallback> = new Set()
   private currentSrc = ''
   private preloaded: Map<'A' | 'B', string> = new Map()
   private switching = false
@@ -50,6 +50,7 @@ export class VideoManager {
     }
     this.elA = null
     this.elB = null
+    this.onTimeCallbacks.clear()
   }
 
   playInitial(src: string, preloadUrls: string[]) {
@@ -141,7 +142,11 @@ export class VideoManager {
   }
 
   onTimeUpdate(cb: TimeUpdateCallback) {
-    this.onTimeCallback = cb
+    this.onTimeCallbacks.add(cb)
+  }
+
+  offTimeUpdate(cb: TimeUpdateCallback) {
+    this.onTimeCallbacks.delete(cb)
   }
 
   private waitReady(el: HTMLVideoElement): Promise<void> {
@@ -160,7 +165,8 @@ export class VideoManager {
 
   private handleTimeUpdate = () => {
     if (this.active) {
-      this.onTimeCallback?.(this.active.currentTime)
+      const t = this.active.currentTime
+      this.onTimeCallbacks.forEach((cb) => cb(t))
     }
   }
 }