Fix MCP tools count update in plug icon indicator

- Add onMcpToolsUpdate prop to ConversationThread interface
- Pass setMcpTools function from ChatApp down to ConversationThread
- Connect McpServerModal onToolsUpdate to parent state update
- Now plug icon will correctly show '1 (N)' when N tools are available
- Fixes issue where tool count remained at 0 despite successful connection

examples/chat-ui/src/components/ChatApp.tsx

@@ -143,6 +143,7 @@ const ChatApp: React.FC<ChatAppProps> = () => {
             onModelChange={handleModelChange}
             apiKeyUpdateTrigger={apiKeyUpdateTrigger}
             mcpTools={mcpTools}
+            onMcpToolsUpdate={setMcpTools}
           />
         </div>
       </div>