feat: support multi-select and batch export in path list

- DataGrid: SelectionMode Extended with RowStyle IsSelected binding
- PathRouteViewModel: add IsSelected property
- Export: iterates selected paths, saves each to separate file
- Ctrl/Shift+click to multi-select, then Export button batches them

src/UI/WPF/Models/PathRouteViewModel.cs

@@ -183,6 +183,7 @@ namespace NavisworksTransport.UI.WPF.ViewModels
         private string _name;
         private ObservableCollection<PathPointViewModel> _points;
         private bool _isActive;
+        private bool _isSelected;
         private string _description;
         private DateTime _createdTime;
         private DateTime _lastModifiedTime;
@@ -313,6 +314,15 @@ namespace NavisworksTransport.UI.WPF.ViewModels
             }
         }
 
+        /// <summary>
+        /// 是否被选中（DataGrid多选绑定）
+        /// </summary>
+        public bool IsSelected
+        {
+            get => _isSelected;
+            set => SetProperty(ref _isSelected, value);
+        }
+
         /// <summary>
         /// 路径描述
         /// </summary>

src/UI/WPF/Views/PathEditingView.xaml

@@ -42,6 +42,11 @@ NavisworksTransport 路径编辑页签视图 - 采用与动画控制和分层管
                 <Setter Property="Foreground" Value="{StaticResource NavisworksSecondaryBrush}"/>
                 <Setter Property="Height" Value="20"/>
             </Style>
+
+            <!-- 可多选的DataGrid行样式 -->
+            <Style x:Key="SelectableRowStyle" TargetType="DataGridRow">
+                <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
+            </Style>
         </ResourceDictionary>
     </UserControl.Resources>
 
@@ -241,7 +246,8 @@ NavisworksTransport 路径编辑页签视图 - 采用与动画控制和分层管
                               AutoGenerateColumns="False"
                               CanUserAddRows="False"
                               CanUserDeleteRows="False"
-                              SelectionMode="Single"
+                              SelectionMode="Extended"
+                              RowStyle="{StaticResource SelectableRowStyle}"
                               HeadersVisibility="Column"
                               GridLinesVisibility="Horizontal"
                               Height="340"