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 `///`).

game_template/lib/main.dart

@@ -129,19 +129,16 @@ class MyApp extends StatelessWidget {
     routes: [
       GoRoute(
         path: '/',
-        builder:
-            (context, state) => const MainMenuScreen(key: Key('main menu')),
+        builder: (context, state) =>
+            const MainMenuScreen(key: Key('main menu')),
         routes: [
           GoRoute(
             path: 'play',
-            pageBuilder:
-                (context, state) => buildMyTransition<void>(
-                  key: ValueKey('play'),
-                  child: const LevelSelectionScreen(
-                    key: Key('level selection'),
-                  ),
-                  color: context.watch<Palette>().backgroundLevelSelection,
-                ),
+            pageBuilder: (context, state) => buildMyTransition<void>(
+              key: ValueKey('play'),
+              child: const LevelSelectionScreen(key: Key('level selection')),
+              color: context.watch<Palette>().backgroundLevelSelection,
+            ),
             routes: [
               GoRoute(
                 path: 'session/:level',
@@ -190,8 +187,8 @@ class MyApp extends StatelessWidget {
           ),
           GoRoute(
             path: 'settings',
-            builder:
-                (context, state) => const SettingsScreen(key: Key('settings')),
+            builder: (context, state) =>
+                const SettingsScreen(key: Key('settings')),
           ),
         ],
       ),
@@ -238,10 +235,9 @@ class MyApp extends StatelessWidget {
           ),
           Provider<SettingsController>(
             lazy: false,
-            create:
-                (context) =>
-                    SettingsController(persistence: settingsPersistence)
-                      ..loadStateFromPersistence(),
+            create: (context) =>
+                SettingsController(persistence: settingsPersistence)
+                  ..loadStateFromPersistence(),
           ),
           ProxyProvider2<
             SettingsController,