[feat] markdown links should spawn browser by default when clicked

Hi,

i found that the markdown url syntax just shown with title, no url highlight, and i cant click on it

```
# markdown syntax example
[link-title](https://google.com/)
```
which should shown like

[link-title](https://google.com/)

but it only show below, and not clickable

link-title

envrionments:
ios 18.5
flutter: Flutter 3.29.3 • channel stable • https://github.com/flutter/flutter.git
Framework • revision ea121f8859 (4 months ago) • 2025-04-11 19:10:07 +0000
Engine • revision cf56914b32
Tools • Dart 3.7.2 • DevTools 2.42.3

the minimal repro

```
import 'package:flutter/material.dart';
import 'package:flutter_ai_toolkit/flutter_ai_toolkit.dart';

class TestOverflowScreen extends StatefulWidget {
const TestOverflowScreen({super.key});

@override
State createState() => _TestOverflowScreenState();
}

class _TestOverflowScreenState extends State {

@override
Widget build(BuildContext context) {
return Scaffold(
body: LlmChatView(
provider: EchoProvider(),
),
);
}
}
```

thx !