feat: 选区截图时保留屏幕笔迹 (#406)

* feat: 使用选区截图时，不清除 Strokes（Keep it on screen）

* fix: 浮动栏选区截图前强制保持墨迹可见

* fix: 避免选区截图回滚 inkCanvas 运行时状态

* fix: 截图前退出并在结束后恢复批注状态

* fix: 截图流程改用轻量批注暂停避免副作用

* feat: 选区截图添加包含墨迹开关

* fix: 避免选区截图墨迹重复渲染

* fix: 全屏基础截图排除主窗口后再叠加墨迹

* fix: 隐藏浮动栏后再进入选区截图

* fix: 添加到白板时不强制恢复浮动栏可见性

* fix: 防止重复启动选区截图实例

* fix: 仅在白板接管成功后跳过浮动栏恢复

* feat: 选区截图时实时预览包含墨迹开关

* fix: 合并截图选择器OnClosed逻辑避免重复定义

Ink Canvas/Windows/ScreenshotSelectorWindow.xaml

@@ -139,6 +139,17 @@
                 <Separator Style="{StaticResource {x:Static ToolBar.SeparatorStyleKey}}" 
                           Margin="8,0" 
                           Background="#404040" />
+
+                <!-- 选项开关 -->
+                <CheckBox Name="IncludeInkCheckBox"
+                          Content="包含墨迹"
+                          IsChecked="True"
+                          Margin="8,0"
+                          VerticalAlignment="Center"
+                          Foreground="White"
+                          FontWeight="Medium"
+                          Checked="IncludeInkCheckBox_Checked"
+                          Unchecked="IncludeInkCheckBox_Unchecked" />
                 
                 <!-- 操作按钮 -->
                 <Button Name="ConfirmButton"

Ink Canvas/Windows/ScreenshotSelectorWindow.xaml.cs

@@ -37,6 +37,7 @@ namespace Ink_Canvas
         private Bitmap _capturedCameraImage = null;
         private DateTime _lastBlankClickTime = DateTime.MinValue;
         private WpfPoint _lastBlankClickPosition;
+        private readonly Action<bool> _includeInkPreviewChanged;
 
         private const int DoubleClickTimeThresholdMs = 300; // 双击判定时间阈值（常见范围 200~500ms）
         private const double DoubleClickDistanceThresholdPx = 12; // 双击判定位置阈值（像素）
@@ -55,10 +56,17 @@ namespace Ink_Canvas
         public Bitmap CameraImage { get; private set; }
         public System.Windows.Media.Imaging.BitmapSource CameraBitmapSource { get; private set; }
         public bool ShouldAddToWhiteboard { get; private set; }
+        public bool ShouldIncludeInk { get; private set; } = true;
 
         public ScreenshotSelectorWindow()
+            : this(null)
+        {
+        }
+
+        public ScreenshotSelectorWindow(Action<bool> includeInkPreviewChanged)
         {
             InitializeComponent();
+            _includeInkPreviewChanged = includeInkPreviewChanged;
 
             // 设置窗口覆盖所有屏幕
             SetupFullScreenOverlay();
@@ -84,6 +92,8 @@ namespace Ink_Canvas
                 timer.Stop();
             };
             timer.Start();
+
+            ApplyIncludeInkPreviewState(ShouldIncludeInk);
         }
 
         private void InitializeFreehandMode()
@@ -529,6 +539,30 @@ namespace Ink_Canvas
             ConfirmSelection();
         }
 
+        private void IncludeInkCheckBox_Checked(object sender, RoutedEventArgs e)
+        {
+            ShouldIncludeInk = true;
+            ApplyIncludeInkPreviewState(ShouldIncludeInk);
+        }
+
+        private void IncludeInkCheckBox_Unchecked(object sender, RoutedEventArgs e)
+        {
+            ShouldIncludeInk = false;
+            ApplyIncludeInkPreviewState(ShouldIncludeInk);
+        }
+
+        private void ApplyIncludeInkPreviewState(bool shouldIncludeInk)
+        {
+            try
+            {
+                _includeInkPreviewChanged?.Invoke(shouldIncludeInk);
+            }
+            catch (Exception ex)
+            {
+                LogHelper.WriteLogToFile($"更新“包含墨迹”实时预览失败: {ex.Message}", LogHelper.LogType.Warning);
+            }
+        }
+
         private void ConfirmCameraCapture()
         {
             try
@@ -1480,6 +1514,9 @@ namespace Ink_Canvas
         {
             try
             {
+                // 关闭窗口时恢复墨迹预览状态
+                ApplyIncludeInkPreviewState(true);
+
                 // 清理摄像头资源
                 if (_cameraService != null)
                 {