Phase 2-3: UI layout, theme switching, CRUD tools, process execution

- Phase 2: MainWindow 3-section layout (sidebar/content/log bar), Dark/Light theme with ThemeHelper, MainViewModel with ObservableProperty/RelayCommand, tool card filtering by search + category

- Phase 3: ToolEditWindow for add/edit tools, ProcessExecutionService (Process.Start + error handling), double-click + right-click context menu (run/edit), path browse dialog

- Bugfix: ContextMenu commands now use PlacementTarget.Tag binding (ContextMenu in separate visual tree)

- Bugfix: StaticResource converters moved to XAML before DataTemplate to fix XamlParseException on tool card render

- Bugfix: Pure filenames (no path separators) treated as PATH commands, not marked invalid

- Bugfix: RefreshData preserves SelectedCategory; Load() catches all exceptions; Save() wrapped in try-catch; auto-scroll log to newest entry

- Tests: xUnit project with 55 tests covering models, services, converters, and view models

PersonalToolBox/Views/ToolEditWindow.xaml.cs

@@ -0,0 +1,21 @@
+using System.Windows;
+using PersonalToolBox.ViewModels;
+
+namespace PersonalToolBox.Views;
+
+public partial class ToolEditWindow : Window
+{
+    public ToolEditWindow(ToolEditViewModel viewModel)
+    {
+        InitializeComponent();
+
+        viewModel.CloseAction = (result) =>
+        {
+            // DialogResult 会自动关闭由 ShowDialog() 显示的窗口，无需显式调用 Close()
+            DialogResult = result;
+        };
+
+        Owner = Application.Current.MainWindow;
+        DataContext = viewModel;
+    }
+}