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_counter/lib/main.dart

@@ -32,7 +32,8 @@ const double windowWidth = 360;
 const double windowHeight = 640;
 
 void setupWindow() {
-  if (!kIsWeb && (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
+  if (!kIsWeb &&
+      (Platform.isWindows || Platform.isLinux || Platform.isMacOS)) {
     WidgetsFlutterBinding.ensureInitialized();
     setWindowTitle('Provider Counter');
     setWindowMinSize(const Size(windowWidth, windowHeight));
@@ -92,11 +93,10 @@ class MyHomePage extends StatelessWidget {
             // Then it uses that model to build widgets, and will trigger
             // rebuilds if the model is updated.
             Consumer<Counter>(
-              builder:
-                  (context, counter, child) => Text(
-                    '${counter.value}',
-                    style: Theme.of(context).textTheme.headlineMedium,
-                  ),
+              builder: (context, counter, child) => Text(
+                '${counter.value}',
+                style: Theme.of(context).textTheme.headlineMedium,
+              ),
             ),
           ],
         ),

provider_counter/pubspec.yaml

@@ -3,14 +3,14 @@ description: >
   The starter Flutter application, but using Provider to manage state.
 publish_to: none
 version: 1.0.0
+resolution: workspace
 
 environment:
-  sdk: ^3.7.0-0
+  sdk: ^3.9.0-0
 
 dependencies:
   flutter:
     sdk: flutter
-
   provider: ^6.0.2
   cupertino_icons: ^1.0.3
   window_size:
@@ -23,6 +23,5 @@ dev_dependencies:
     path: ../analysis_defaults
   flutter_test:
     sdk: flutter
-
 flutter:
   uses-material-design: true