Widget Preview Documentation and PreviewThemeData API are out-of-sync

On official Flutter Documentation for widget previews the APIs mentioned for providing custom theme data to widget preview is not accurate.

Filter previews by selected file in IDEs: [Example flutter/flutter#1](https://docs.flutter.dev/tools/widget-previewer#filter-previews-by-selected-file-in-ides)
Create custom preview annotations: [Example flutter/flutter#2](https://docs.flutter.dev/tools/widget-previewer#create-custom-preview-annotations)

Both of these examples describe the API for `PreviewThemeData` to be something like this:
```dart
PreviewThemeData(
materialLight: ThemeData.light(),
materialDark: ThemeData.dark(),
);
```

However as of `Flutter 3.47` according to [api.flutter.dev#PreviewThemeData](https://api.flutter.dev/flutter/widget_previews/PreviewThemeData-class.html) the `PreviewThemeData` is mentioned as a `zero argument interface`.

This is a massive disconnect between what is shown and what is currently available. There are many other similar examples showcasing the same usage.

```text
[!] Flutter (Channel stable, 3.47.0, on macOS 15.7.8 24G812 darwin-x64, locale en-IN) [2.8s]
! Flutter is deprecating support for Intel-based Macs. A future version of Flutter will require an Apple Silicon Mac to
build applications.
• Flutter version 3.47.0 on channel stable at /opt/maranix/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 4cf2416426 (7 days ago), 2026-08-11 11:53:49 -0700
• Engine revision 5f77625673
• Dart version 3.13.0
• DevTools version 2.60.0
• Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android,
enable-ios, cli-animations, enable-native-assets, enable-record-use, enable-swift-package-manager,
omit-legacy-version-file, enable-lldb-debugging, enable-uiscene-migration
• If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly to
perform update checks and upgrades.

[✓] Android toolchain - develop for Android devices (Android SDK version 37.0.0) [11.6s]
• Android SDK at /opt/maranix/Android/Sdk
• Emulator version unknown
• Platform android-37.0, build-tools 37.0.0
• ANDROID_HOME = /opt/maranix/Android/Sdk/
• Java binary at: /usr/bin/java
This JDK was found in the system PATH.
To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
• Java version OpenJDK Runtime Environment Temurin-25.0.4+7 (build 25.0.4+7-LTS)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 26.2) [9.8s]
• Xcode at /Applications/Xcode.app/Contents/Developer
• Build 17C52
• CocoaPods version 1.16.2

[✓] Chrome - develop for the web [647ms]
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (3 available) [13.1s]
• Raman’s iPhone (wireless) (mobile) • 00008120-00025DDE14C3A01E • ios • iOS 26.6 23G71
• macOS (desktop) • macos • darwin-x64 • macOS 15.7.8 24G812 darwin-x64
• Chrome (web) • chrome • web-javascript • Google Chrome 151.0.7922.138
! Unexpected failure parsing device information from adb output:
adb-1603546865001HB-2xZ2LU._adb-tls-connect._tcp device product:2127i model:V2142 device:2127 transport_id:1
Please report a bug at https://github.com/flutter/flutter/issues.

[✓] Network resources [1,325ms]
• All expected network resources are available.

! Doctor found issues in 1 category.
```

Start with the widget preview documentation sections “Filter previews by selected file in IDEs” and “Create custom preview annotations,” then compare their PreviewThemeData examples with the linked API reference. Update the affected examples and similar usages so they match the current API, and verify that the documentation no longer shows unsupported arguments.

Written by the indexing model from the issue text.