fix: CV 视觉组件截屏脚本补加载 System.Windows.Forms

- grabScreen 只 Add-Type 了 System.Drawing, 引用 Windows.Forms.Screen 却未加载该程序集
- 导致 PrimaryScreen.Bounds 取值为 Null, 截屏链路 InvokeMethodOnNull, 所有 CV_* 组件运行失败
- 与 remaining-core.ts 中正常工作的同款脚本对齐

src/main/capabilities/cv-vision.ts

@@ -27,6 +27,7 @@ async function grabScreen(imagePath: string): Promise<void> {
   fs.mkdirSync(path.dirname(imagePath), { recursive: true });
   const psScript = [
     "Add-Type -AssemblyName System.Drawing | Out-Null;",
+    "Add-Type -AssemblyName System.Windows.Forms | Out-Null;",
     "$b = [System.Windows.Forms.Screen]::PrimaryScreen.Bounds;",
     "$bmp = New-Object System.Drawing.Bitmap($b.Width, $b.Height);",
     "$g = [System.Drawing.Graphics]::FromImage($bmp);",