feat: drag&drop treeview, flat chat UI, activity indicator, fixed toolbar registration

frontend/src/pages/AIAssistant.tsx

@@ -15,8 +15,30 @@ export function AIAssistantPage() {
 
   useEffect(() => {
     registerItems('ai_assistant', [
-      { id: 'agent-select', label: 'Agent', type: 'select', options: agents.map((a) => ({ value: a.id, label: a.name })), value: selectedAgentId || '', onChange: (val: string) => setSelectedAgentId(val || null) },
-      { id: 'new-chat', label: 'Neuer Chat', type: 'button', onClick: () => { setActiveSessionId(null); setMobileView('list'); } },
+      {
+        id: 'agent-select',
+        plugin: 'ai_assistant',
+        label: 'Agent',
+        type: 'select',
+        group: 'agent',
+        selectOptions: agents.map((a) => ({ value: a.id, label: a.name })),
+        selectValue: selectedAgentId || '',
+        onSelect: (val: string) => setSelectedAgentId(val || null),
+        onClick: () => {},
+      },
+      {
+        id: 'new-chat',
+        plugin: 'ai_assistant',
+        label: 'Neuer Chat',
+        type: 'button',
+        group: 'actions',
+        icon: (
+          <svg className="w-3.5 h-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 4v16m8-8H4" />
+          </svg>
+        ),
+        onClick: () => { setActiveSessionId(null); setMobileView('list'); },
+      },
     ]);
     return () => unregisterPlugin('ai_assistant');
   }, [agents, selectedAgentId, registerItems, unregisterPlugin]);