fix: Neuer Chat Button erstellt Session, Ordner drag&drop im KI-Baum

frontend/src/pages/AIAssistant.tsx

@@ -3,7 +3,7 @@ import { SessionList } from '@/components/ai/SessionList';
 import { ChatWindow } from '@/components/ai/ChatWindow';
 import { ResizablePanel } from '@/components/ui/ResizablePanel';
 import { usePluginToolbarStore } from '@/store/pluginToolbarStore';
-import { fetchAgents, type AIAgent } from '@/api/ai';
+import { fetchAgents, createSession, type AIAgent } from '@/api/ai';
 
 export function AIAssistantPage() {
   const [activeSessionId, setActiveSessionId] = useState<string | null>(null);
@@ -39,7 +39,16 @@ export function AIAssistantPage() {
             <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 4v16m8-8H4" />
           </svg>
         ),
-        onClick: () => { setActiveSessionId(null); setMobileView('list'); setRefreshKey(k => k + 1); },
+        onClick: async () => {
+          try {
+            const session = await createSession({ is_sidebar: false });
+            setActiveSessionId(session.id);
+            setMobileView('chat');
+            setRefreshKey(k => k + 1);
+          } catch (e) {
+            console.error('Failed to create session:', e);
+          }
+        },
       },
       {
         id: 'new-folder',