feat: add minimal flutter hello world sample (#3512)

Author: NamanGoyalK

pkgs/dartpad_ui/lib/primitives/samples.g.dart

@@ -8,11 +8,12 @@ Sample code snippets for DartPad.
 | Category | Name | Sample | ID |
 | --- | --- | --- | --- |
 | Dart | Fibonacci | [fibonacci.dart](lib/fibonacci.dart) | `fibonacci` |
-| Dart | Hello world | [hello_world.dart](lib/hello_world.dart) | `hello-world` |
+| Dart | Hello world | [hello_world_dart.dart](lib/hello_world_dart.dart) | `hello-world-dart` |
 | Defaults | Dart snippet | [default_dart.dart](lib/default_dart.dart) | `dart` |
 | Defaults | Flutter snippet | [default_flutter.dart](lib/default_flutter.dart) | `flutter` |
 | Ecosystem | Flame game | [brick_breaker.dart](lib/brick_breaker.dart) | `flame-game` |
 | Flutter | Counter | [main.dart](lib/main.dart) | `counter` |
+| Flutter | Hello world | [hello_world_flutter.dart](lib/hello_world_flutter.dart) | `hello-world-flutter` |
 | Flutter | Sunflower | [sunflower.dart](lib/sunflower.dart) | `sunflower` |
 <!-- samples -->
 

pkgs/samples/README.md

@@ -0,0 +1,20 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(const MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return const MaterialApp(
+      home: Scaffold(body: Center(child: Text('Hello World'))),
+    );
+  }
+}

pkgs/samples/lib/hello_world.dart pkgs/samples/lib/hello_world_dart.dartpkgs/samples/lib/hello_world.dart renamed to pkgs/samples/lib/hello_world_dart.dart

@@ -16,8 +16,9 @@
   {
     "category": "Dart",
     "icon": "dart",
+    "id": "hello-world-dart",
     "name": "Hello world",
-    "path": "lib/hello_world.dart"
+    "path": "lib/hello_world_dart.dart"
   },
   {
     "category": "Dart",
@@ -37,6 +38,13 @@
     "name": "Sunflower",
     "path": "lib/sunflower.dart"
   },
+  {
+    "category": "Flutter",
+    "icon": "flutter",
+    "id": "hello-world-flutter",
+    "name": "Hello world",
+    "path": "lib/hello_world_flutter.dart"
+  },
   {
     "category": "Ecosystem",
     "icon": "flame",