fix: Canvas标题居中 - video offsetX补偿 + 闭包修复

- drawTitleOnCanvas新增offsetX参数补偿video offsetLeft
- drawVideoTitle传入videoEl.offsetLeft作为居中偏移
- 将drawVideoTitle/drawNoVideoTitle加入font-loading effect deps
- 移除eslint-disable，正确处理闭包依赖
- titleText变化时effect重新执行，使用最新回调

apps/web/src/pages/generate/components/PreviewVideoPanel.tsx

@@ -54,6 +54,7 @@ function wrapText(ctx: CanvasRenderingContext2D, text: string, maxWidth: number)
  * @param position "top" | "center" | "bottom"
  * @param topOffset 顶部/底部偏移量
  * @param fontSizeScale 字号缩放（no-video 模式下缩小）
+ * @param offsetX 绘制区域左边缘相对于 canvas 的偏移（用于 video 居中时补偿 offsetLeft）
  */
 function drawTitleOnCanvas(
   ctx: CanvasRenderingContext2D,
@@ -65,6 +66,7 @@ function drawTitleOnCanvas(
   position: string,
   topOffset: number,
   fontSizeScale = 1,
+  offsetX = 0,
 ) {
   const dpr = window.devicePixelRatio || 1
   const w = canvasWidth
@@ -128,8 +130,8 @@ function drawTitleOnCanvas(
       break
   }
 
-  // 逐行绘制（水平居中于绘制区域）
-  const x = w / 2
+  // 逐行绘制（offsetX 补偿 video 在容器内的居中偏移）
+  const x = offsetX + w / 2
   lines.forEach((line, i) => {
     const y = startY + i * lineHeight
     if (settings.stroke) ctx.strokeText(line, x, y)
@@ -204,6 +206,8 @@ export const PreviewVideoPanel: React.FC<PreviewVideoPanelProps> = ({
       40,
       titleSettings.position,
       60,
+      1,
+      videoEl ? videoEl.offsetLeft : 0,
     )
   }, [titleText, titleSettings])
 
@@ -304,10 +308,7 @@ export const PreviewVideoPanel: React.FC<PreviewVideoPanelProps> = ({
     return () => {
       cancelled = true
     }
-    // drawVideoTitle/drawNoVideoTitle 通过 fontLoadedRef 读取字体状态，
-    // 不依赖 fontLoaded state，无需加入 deps
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [showTitlePreview, titleSettings])
+  }, [showTitlePreview, titleSettings, drawVideoTitle, drawNoVideoTitle])
 
   // video 加载完成后重绘
   const handleVideoLoaded = useCallback(() => {