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/Services/JsonDataService.cs

@@ -65,11 +65,22 @@ public class JsonDataService : IDataService
                     continue;
                 }
 
+                // 纯文件名（无路径分隔符）可能位于系统 PATH 中，不标记为失效
+                if (!tool.ExecutablePath.Contains('\\') && !tool.ExecutablePath.Contains('/'))
+                {
+                    tool.IsValid = true;
+                    continue;
+                }
+
                 if (!File.Exists(tool.ExecutablePath))
                 {
                     tool.IsValid = false;
                     _logService.Warning($"工具 \"{tool.Name}\" 路径失效，找不到文件: {tool.ExecutablePath}");
                 }
+                else
+                {
+                    tool.IsValid = true;
+                }
             }
 
             _logService.Info($"配置加载完成: {Config.Categories.Count} 个分类, {Config.Tools.Count} 个工具");
@@ -79,6 +90,11 @@ public class JsonDataService : IDataService
             _logService.Error($"配置文件 JSON 解析失败: {ex.Message}");
             Config = new AppConfig();
         }
+        catch (Exception ex)
+        {
+            _logService.Error($"配置文件加载失败: {ex.Message}");
+            Config = new AppConfig();
+        }
     }
 
     public void Save()