Dart 3.9 / Flutter 3.35 [first LLM release] (#2714)

I got carried away with Gemini and basically rewrote CI and the release
process for the new LLM reality. This work was largely completed by
Gemini.

- Bump all SDK versions to the current beta (3.9.0-0)
- Run `flutter channel beta`
- Wrote `ci_script.dart` to replace the bash scripts
- Converted repository to pub workspace #2499 
- Added llm.md and release.md
- Added redirect for deprecated Samples Index

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).

navigation_and_routing/lib/src/screens/authors.dart

@@ -12,7 +12,11 @@ class AuthorsScreen extends StatelessWidget {
   final String title;
   final ValueChanged<Author> onTap;
 
-  const AuthorsScreen({required this.onTap, this.title = 'Authors', super.key});
+  const AuthorsScreen({
+    required this.onTap,
+    this.title = 'Authors',
+    super.key,
+  });
 
   @override
   Widget build(BuildContext context) => Scaffold(