fix: Web端投屏画面缩小闪烁问题

- canvas尺寸锁定策略：首次有效帧锁定canvas尺寸，后续帧统一drawImage缩放绘制
- 消除不同采集模式(MediaProjection/无障碍截图)帧尺寸不一致导致的canvas反复resize
- 设备切换或断开时重置锁定尺寸，下次连接重新锁定
- 移除renderLatestFrame对screenDisplay.fitMode的无效依赖

src/components/Device/DeviceScreen.tsx

@@ -38,10 +38,9 @@ const DeviceScreen: React.FC<DeviceScreenProps> = ({ deviceId, onScreenSizeChang
   const isRenderingRef = useRef(false)
   const imageSizeRef = useRef<{ width: number, height: number } | null>(null)
   
-  // ✅ 尺寸稳定性：防止偶发异常帧导致canvas闪烁
-  const pendingSizeRef = useRef<{ width: number, height: number } | null>(null)
-  const pendingSizeCountRef = useRef(0)
-  const SIZE_STABLE_THRESHOLD = 3 // 连续3帧相同尺寸才更新
+  // canvas锁定尺寸：首次有效帧确定canvas尺寸后不再变化，
+  // 避免不同采集模式(MediaProjection/无障碍截图)帧尺寸不一致导致闪烁
+  const lockedCanvasSizeRef = useRef<{ width: number, height: number } | null>(null)
   
   // ✅ 添加控制权状态跟踪，避免重复申请
   const [isControlRequested, setIsControlRequested] = useState(false)
@@ -172,6 +171,8 @@ const DeviceScreen: React.FC<DeviceScreenProps> = ({ deviceId, onScreenSizeChang
         rafIdRef.current = 0
       }
       isRenderingRef.current = false
+      // 设备切换或断开时重置锁定尺寸，下次连接重新锁定
+      lockedCanvasSizeRef.current = null
     }
   }, [webSocket, deviceId])
 
@@ -303,52 +304,33 @@ const DeviceScreen: React.FC<DeviceScreenProps> = ({ deviceId, onScreenSizeChang
             return
           }
 
-          // canvas尺寸匹配bitmap，只在尺寸真正变化时才设置
-          // 注意：设置canvas.width/height会清空画布内容，所以必须紧接着绘制新帧
-          const needsResize = canvas.width !== bitmap.width || canvas.height !== bitmap.height
-          if (needsResize) {
+          // canvas尺寸锁定策略：
+          // 首次有效帧确定canvas尺寸后锁定，后续帧直接绘制到固定尺寸canvas上
+          // 避免不同采集模式帧尺寸不一致导致canvas反复resize闪烁
+          const locked = lockedCanvasSizeRef.current
+          if (!locked) {
+            // 首次帧：锁定canvas尺寸
+            lockedCanvasSizeRef.current = { width: bitmap.width, height: bitmap.height }
             canvas.width = bitmap.width
             canvas.height = bitmap.height
+          } else if (canvas.width !== locked.width || canvas.height !== locked.height) {
+            // canvas被外部重置了，恢复锁定尺寸
+            canvas.width = locked.width
+            canvas.height = locked.height
           }
 
-          switch (screenDisplay.fitMode) {
-            case 'fit':
-              drawFitMode(ctx, bitmap, canvas)
-              break
-            case 'fill':
-              drawFillMode(ctx, bitmap, canvas)
-              break
-            case 'stretch':
-              drawStretchMode(ctx, bitmap, canvas)
-              break
-            case 'original':
-              drawOriginalMode(ctx, bitmap, canvas)
-              break
-          }
+          // 始终将bitmap绘制到整个canvas区域，浏览器自动缩放
+          // 这样不同尺寸的帧都能正确显示，不会闪烁
+          ctx.drawImage(bitmap, 0, 0, canvas.width, canvas.height)
 
-          const bw = bitmap.width
-          const bh = bitmap.height
+          // 使用锁定的canvas尺寸上报，保持稳定
+          const reportSize = lockedCanvasSizeRef.current
+          if (reportSize) {
             const prevSize = imageSizeRef.current
-          if (!prevSize || prevSize.width !== bw || prevSize.height !== bh) {
-            // 尺寸稳定性检查：只有连续多帧相同尺寸才更新，防止偶发异常帧闪烁
-            const pending = pendingSizeRef.current
-            if (pending && pending.width === bw && pending.height === bh) {
-              pendingSizeCountRef.current++
-            } else {
-              pendingSizeRef.current = { width: bw, height: bh }
-              pendingSizeCountRef.current = 1
+            if (!prevSize || prevSize.width !== reportSize.width || prevSize.height !== reportSize.height) {
+              imageSizeRef.current = { width: reportSize.width, height: reportSize.height }
+              setImageSize({ width: reportSize.width, height: reportSize.height })
             }
-            
-            if (pendingSizeCountRef.current >= SIZE_STABLE_THRESHOLD || !prevSize) {
-              imageSizeRef.current = { width: bw, height: bh }
-              setImageSize({ width: bw, height: bh })
-              pendingSizeRef.current = null
-              pendingSizeCountRef.current = 0
-            }
-          } else {
-            // 尺寸未变，重置pending
-            pendingSizeRef.current = null
-            pendingSizeCountRef.current = 0
           }
 
           const now = Date.now()
@@ -373,7 +355,7 @@ const DeviceScreen: React.FC<DeviceScreenProps> = ({ deviceId, onScreenSizeChang
     }
 
     doRender()
-  }, [screenDisplay.fitMode])
+  }, [])
 
   const drawFitMode = (ctx: CanvasRenderingContext2D, img: HTMLImageElement | ImageBitmap, canvas: HTMLCanvasElement) => {
     const scale = Math.min(canvas.width / img.width, canvas.height / img.height)