SelectionArea width differs between web and native

### Steps to reproduce

1. Run the code on web and native (screenshots below taken on Linux)
2. Toggle `wrapInSelectionArea` to wrap the dialog content in a `SelectionArea` 
3. Compare the results between web and native

### Expected results

`SelectionArea` extends to the full width of the dialog on both web and desktop.

### Actual results

`SelectionArea` extends to the full width of the dialog on desktop, but not on web.

### Code sample

<details open><summary>Code sample</summary>

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

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: const MyHomePage());
  }
}

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

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  void initState() {
    super.initState();

    WidgetsBinding.instance.addPostFrameCallback((_) {
      showDialog(
        context: context,
        builder: (context) => ChillDialog(
          children: [
            const Text(
              'Welcome to Flutter! This is a simple dialog example. You can add any widgets here. Feel free to customize it as needed.',
            ),
            ElevatedButton(
              child: Text("Close"),
              onPressed: () {
                Navigator.pop(context);
              },
            ),
          ],
        ),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    return Placeholder();
  }
}

class ChillDialog extends StatelessWidget {
  const ChillDialog({this.children = const [], super.key});

  final List<Widget> children;

  @override
  Widget build(BuildContext context) {
    final wrapInSelectionArea = true;

    final content = Container(
      constraints: const BoxConstraints(maxWidth: 250),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: children,
      ),
    );

    return SimpleDialog(
      children: [
        if (wrapInSelectionArea) SelectionArea(child: content) else content,
      ],
    );
  }
}

```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>



With `SelectionArea` (web top, Linux bottom):
<img width="958" height="1031" alt="Image" src="https://github.com/user-attachments/assets/30632c8f-9b2b-480a-9909-2c98e4f212c2" />

Without `SelectionArea` (web top, Linux bottom):
<img width="955" height="1033" alt="Image" src="https://github.com/user-attachments/assets/69f7b1c2-24f0-4508-ace6-7d83e4434bdf" />

</details>


### Logs




### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[✓] Flutter (Channel stable, 3.32.5, on Arch Linux 6.15.4-arch2-1, locale en_US.UTF-8) [101ms]
    • Flutter version 3.32.5 on channel stable at /home/felipe/Applications/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision fcf2c11572 (10 days ago), 2025-06-24 11:44:07 -0700
    • Engine revision dd93de6fb1
    • Dart version 3.8.1
    • DevTools version 2.45.1

[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0-rc2) [2.2s]
    • Android SDK at /home/felipe/Android/Sdk/
    • Platform android-35, build-tools 35.0.0-rc2
    • ANDROID_HOME = ~/Android/Sdk
    • Java binary at: /home/felipe/Applications/android-studio/jbr/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)
    • All Android licenses accepted.

[✓] Chrome - develop for the web [17ms]
    • CHROME_EXECUTABLE = chromium

[✓] Linux toolchain - develop for Linux desktop [408ms]
    • clang version 20.1.6
    • cmake version 4.0.3-dirty
    • ninja version 1.12.1
    • pkg-config version 2.5.1
    • OpenGL core renderer: Mesa Intel(R) Iris(R) Xe Graphics (TGL GT2)
    • OpenGL core version: 4.6 (Core Profile) Mesa 25.1.4-arch1.1
    • OpenGL core shading language version: 4.60
    • OpenGL ES renderer: Mesa Intel(R) Iris(R) Xe Graphics (TGL GT2)
    • OpenGL ES version: OpenGL ES 3.2 Mesa 25.1.4-arch1.1
    • OpenGL ES shading language version: OpenGL ES GLSL ES 3.20
    • GL_EXT_framebuffer_blit: yes
    • GL_EXT_texture_format_BGRA8888: yes

[✓] Android Studio (version 2024.1) [15ms]
    • Android Studio at /home/felipe/Applications/android-studio
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)

[✓] Connected device (2 available) [130ms]
    • Linux (desktop) • linux  • linux-x64      • Arch Linux 6.15.4-arch2-1
    • Chrome (web)    • chrome • web-javascript • Chromium 138.0.7204.49 Arch Linux

[✓] Network resources [289ms]
    • All expected network resources are available.

• No issues found!
```

</details>


Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

SelectionArea width differs between web and native #171632

Steps to reproduce

Expected results

Actual results

Code sample

Screenshots or Video

Logs

Flutter Doctor output

Metadata

Assignees

Labels

Type

Fields

Projects

Milestone

Relationships

Development

Uh oh!

SelectionArea width differs between web and native #171632

Description

Steps to reproduce

Expected results

Actual results

Code sample

Screenshots or Video

Logs

Flutter Doctor output

Metadata

Metadata

Assignees

Labels

Type

Fields

Projects

Milestone

Relationships

Development

Issue actions