task(A4.12): v2 history panel reading undo manager behind flag

frontend/src/App.tsx

@@ -18,6 +18,7 @@ import StatusBar from './components/StatusBar';
 import MobileDrawers from './components/MobileDrawers';
 import BackgroundImport from './components/BackgroundImport';
 import HistoryPanel from './components/HistoryPanel';
+import V2HistoryPanel from './components/V2HistoryPanel';
 import SettingsModal from './components/SettingsModal';
 import InlineTextEditor from './components/InlineTextEditor';
 import { BackgroundService, type BackgroundConfig } from './services/backgroundService';
@@ -1728,7 +1729,11 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
         onApply={handleBgApply}
         backgroundService={bgServiceRef.current}
       />
-      {historyPanelOpen && (
+      {historyPanelOpen && (import.meta.env.VITE_TOOL_DISPATCHER === 'v2' ? (
+        <V2HistoryPanel
+          onClose={() => setHistoryPanelOpen(false)}
+        />
+      ) : (
         <HistoryPanel
           entries={historyEntries}
           onJumpTo={(entryId: string) => {
@@ -1741,7 +1746,7 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
           }}
           onClose={() => setHistoryPanelOpen(false)}
         />
-      )}
+      ))}
       {exportFormatOpen && (
         <div className="export-format-overlay" onClick={() => setExportFormatOpen(false)}>
           <div className="export-format-modal" onClick={(e) => e.stopPropagation()}>