视频导出、时间轴与动作姿势模块

- 视频导出：WebCodecs 逐帧快速导出 MP4（固定分辨率不随视口布局变形），MediaRecorder 兜底
- 时间轴：面板可拖动调高（持久化、固定上限）、关键帧轨道区内滚动、无横向滚动条
- 动作模块：走路/跑步步态曲线（对侧摆臂修复、跑步独立步频、跑姿屈膝曲线、参考校准参数）
- 姿势调节：两级折叠分组、动作偏移联动
- 删除对象时同步清理时间轴轨道

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/editor/canvas/SceneRoot.tsx

@@ -476,6 +476,7 @@ function ObjectSceneNode({
   } | null>(null);
   const updateObjectTransform = useDirectorStore((state) => state.updateObjectTransform);
   const isPlaying = usePlaybackStore((state) => state.isPlaying);
+  const motionTime = usePlaybackStore((state) => state.playhead);
   const isImportedModel = asset?.sourceType === "model";
   const characterLabelKey = `${item.id}:${item.bodyType ?? ""}:${item.characterRig?.rigType ?? ""}`;
   const fallbackCharacterLabelY =
@@ -539,6 +540,8 @@ function ObjectSceneNode({
               color={item.color}
               onLabelAnchorYChange={handleCharacterLabelAnchorYChange}
               rigState={item.characterRig}
+              motionTime={motionTime}
+              characterId={item.id}
             />
           </Suspense>
           {showLabels ? (