fix: 修复画布视口渲染阶段修改引用

移除渲染期间对 viewportRef 的赋值
避免并发渲染被丢弃后残留未提交的视口状态
保留状态更新和动画路径中的引用同步

src/components/image-editor/useImageCanvasViewportControls.ts

@@ -90,8 +90,6 @@ export function useImageCanvasViewportControls({
   } | null>(null);
   const minimapDragFrameRef = useRef<number | null>(null);
 
-  viewportRef.current = viewport;
-
   const cancelViewportAnimation = useCallback(() => {
     if (viewportAnimationFrameRef.current === null) {
       return;