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 `///`).

provider_shopper/lib/screens/login.dart

@@ -17,7 +17,10 @@ class MyLogin extends StatelessWidget {
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: [
-              Text('Welcome', style: Theme.of(context).textTheme.displayLarge),
+              Text(
+                'Welcome',
+                style: Theme.of(context).textTheme.displayLarge,
+              ),
               TextFormField(
                 decoration: const InputDecoration(hintText: 'Username'),
               ),
@@ -30,7 +33,9 @@ class MyLogin extends StatelessWidget {
                 onPressed: () {
                   context.pushReplacement('/catalog');
                 },
-                style: ElevatedButton.styleFrom(backgroundColor: Colors.yellow),
+                style: ElevatedButton.styleFrom(
+                  backgroundColor: Colors.yellow,
+                ),
                 child: const Text('ENTER'),
               ),
             ],