feat: 包围盒图标改为双立方体线框样式，与剖面盒图标风格统一

src/UI/WPF/Resources/NavisworksStyles.xaml

@@ -212,8 +212,8 @@ NavisworksTransport 共享样式资源字典 - Navisworks 2026风格
     <!-- L形转角图标 (过弯检测) -->
     <Geometry x:Key="CornerCheckIconGeometry">M2,18 L2,4 L16,4 L16,2 M4,16 L4,6 L14,6 M7,12 L7,8 L11,8 L11,12 Z</Geometry>
 
-    <!-- 包围盒图标 -->
-    <Geometry x:Key="BoundingBoxIconGeometry">M3,3 L17,3 L17,17 L3,17 Z M3,9 L17,9</Geometry>
+    <!-- 包围盒图标 (双线框立方体) -->
+    <Geometry x:Key="BoundingBoxIconGeometry">M3,7 L14,7 L14,18 L3,18 Z M3,7 L7,3 L18,3 L14,7 M14,18 L18,14 L18,3 L14,7 M6,10 L11,10 L11,15 L6,15 Z M6,10 L9,7 L14,7 L11,10 M11,15 L14,12 L14,7 L11,10</Geometry>
 
     <!-- 靶心/准心图标 (测量工具) -->
     <Geometry x:Key="TargetIconGeometry">

src/UI/WPF/Views/PathEditingView.xaml

@@ -322,7 +322,9 @@ NavisworksTransport 路径编辑页签视图 - 采用与动画控制和分层管
                                 Height="24"
                                 Margin="0,0,2,0">
                             <Path Data="{StaticResource BoundingBoxIconGeometry}" 
-                                  Fill="{StaticResource NavisworksPrimaryBrush}" 
+                                  Stroke="{StaticResource NavisworksPrimaryBrush}" 
+                                  StrokeThickness="1.2"
+                                  Fill="Transparent"
                                   Width="16" Height="16" Stretch="Uniform"/>
                         </Button>
                         <Button Grid.Column="2"