fix: demuxSegment添加5秒超时保护+防重复resolve，确保Promise必定resolve

- 添加 resolved 标志位，防止多次 resolve
- 5秒超时保护：onSamples 未触发时 resolve(null)
- 所有 resolve 路径前加 clearTimeout + resolved = true
- onSamples 开头检查 resolved，防止重复处理

apps/web/src/pages/generate/hooks/useCanvasPlayer.ts

@@ -277,11 +277,25 @@ export function useCanvasPlayer(
 
       return new Promise<SegmentMeta | null>((resolve) => {
         let meta: SegmentMeta | null = null
+        let resolved = false
+
+        // ✅ 超时保护：5秒后如果 onSamples 没有触发，返回 null
+        const timeout = setTimeout(() => {
+          if (!resolved) {
+            console.error(
+              `[useCanvasPlayer] Timeout: onSamples not triggered for segment ${segIndex}`,
+            )
+            resolved = true
+            resolve(null)
+          }
+        }, 5000)
 
         mp4File.onReady = (info: Movie) => {
           const videoTrack = info?.videoTracks?.[0]
           if (!videoTrack) {
             console.warn("[useCanvasPlayer] No video track found for segment", segIndex)
+            clearTimeout(timeout)
+            resolved = true
             resolve(null)
             return
           }
@@ -324,7 +338,11 @@ export function useCanvasPlayer(
         }
 
         mp4File.onSamples = (_trackId: number, _user: unknown, samples: Sample[]) => {
+          if (resolved) return // ✅ 防止重复 resolve
+
           if (!meta) {
+            clearTimeout(timeout)
+            resolved = true
             resolve(null)
             return
           }
@@ -368,11 +386,15 @@ export function useCanvasPlayer(
           )
 
           // ✅ 关键修复：等待 onSamples 完成后再返回
+          clearTimeout(timeout)
+          resolved = true
           resolve(meta)
         }
 
         mp4File.onError = (_module: string, message: string) => {
           console.error(`[useCanvasPlayer] MP4Box error: ${message}`)
+          clearTimeout(timeout)
+          resolved = true
           resolve(null)
         }