🐛 fix(workbench): 统一 v2 工具中心与工作区主题

- 显式传递 uiVersion 构建 overlay theme，避免设置中心和工具中心混用旧版黄蓝色
- 统一 v2 模式下 Ant Design 主色和选中态为绿色语义
- 移除工具中心详情头部重复的返回上一步按钮
- 修复侧边树对象筛选反复切换时的 rc-tree 复用漂移
- 调整 v2 左侧树横向滚动条与首页空态布局，释放工作区展示空间
- 补充工具中心、主题 token 和侧边树 remount 的回归测试

frontend/src/hooks/useAppUtilityStyles.tsx

@@ -7,6 +7,7 @@ type UseAppUtilityStylesOptions = {
   darkMode: boolean;
   effectiveOpacity: number;
   effectiveUiScale: number;
+  isV2Ui: boolean;
   resolvedAppearance: {
     opacity: number;
     blur: number;
@@ -19,6 +20,7 @@ export const useAppUtilityStyles = ({
   darkMode,
   effectiveOpacity,
   effectiveUiScale,
+  isV2Ui,
   resolvedAppearance,
   sidebarWidth,
 }: UseAppUtilityStylesOptions) => {
@@ -87,8 +89,11 @@ export const useAppUtilityStyles = ({
   }), [effectiveBlurFilter, darkMode, effectiveUiScale, isOpaqueUtilityMode, isSidebarCompact, utilityButtonBgColor, utilityButtonBorderColor, utilityButtonShadow]);
   const disableLocalBackdropFilter = isMacLikePlatform();
   const overlayTheme = useMemo(
-    () => buildOverlayWorkbenchTheme(darkMode, { disableBackdropFilter: disableLocalBackdropFilter }),
-    [darkMode, disableLocalBackdropFilter],
+    () => buildOverlayWorkbenchTheme(darkMode, {
+      disableBackdropFilter: disableLocalBackdropFilter,
+      uiVersion: isV2Ui ? 'v2' : 'legacy',
+    }),
+    [darkMode, disableLocalBackdropFilter, isV2Ui],
   );
 
   const sidebarQuickActionBaseStyle = useMemo(() => ({