docs: add Flutter Driver example to MCP server page

sites/docs/src/content/ai/mcp-server.md

@@ -392,6 +392,54 @@ is now a single request.
 
 [`package:fl_chart`]: {{site.pub-pkg}}/fl_chart
 
+### Interact with a running app
+
+You can use the Dart and Flutter MCP server to drive a running
+Flutter app from your AI assistant—take screenshots, tap buttons,
+enter text, scroll, and hot reload.
+
+On mobile and desktop, gate `enableFlutterDriverExtension()` behind a
+`--dart-define` flag in your app's `main()` so it stays out of
+production builds:
+
+```dart
+import 'package:flutter_driver/driver_extension.dart';
+
+void main() {
+  if (const bool.fromEnvironment('ENABLE_FLUTTER_DRIVER')) {
+    enableFlutterDriverExtension();
+  }
+  runApp(const MyApp());
+}
+```
+
+Launch your app with the flag turned on:
+
+```bash
+flutter run -d <device-id> --dart-define=ENABLE_FLUTTER_DRIVER=true
+```
+
+Then ask your assistant to connect:
+
+> Connect to my running Flutter app, take a screenshot, then tap "Sign In".
+
+The agent uses the `dtd` tool to discover the app and `flutter_driver_command`
+to drive its UI—no integration test setup required.
+
+:::note
+**Web**: the `flutter_driver` package doesn't compile under dart2js. Pair
+the Dart MCP server with a browser-driving MCP for clicks and screenshots;
+the Dart MCP server still handles widget tree, runtime errors, and hot
+reload through DTD. Prefer `flutter run -d web-server` so the browser the
+agent drives is the one DTD is connected to—with -d chrome, only the
+window Flutter spawned receives hot reload patches.
+
+See the [setup guide][flutter-driver-guide] for the snippet, web modes,
+and common pitfalls.
+:::
+
+[flutter-driver-guide]: https://github.com/dart-lang/ai/blob/main/pkgs/dart_mcp_server/README.md#connect-to-a-running-flutter-app
+
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