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 `///`).

platform_design/lib/main.dart

@@ -56,7 +56,8 @@ class PlatformAdaptingHomePage extends StatefulWidget {
       _PlatformAdaptingHomePageState();
 }
 
-class _PlatformAdaptingHomePageState extends State<PlatformAdaptingHomePage> {
+class _PlatformAdaptingHomePageState
+    extends State<PlatformAdaptingHomePage> {
   // This app keeps a global key for the songs tab because it owns a bunch of
   // data. Since changing platform re-parents those tabs into different
   // scaffolds, keeping a global key to it lets this app keep that tab's data as
@@ -88,7 +89,10 @@ class _PlatformAdaptingHomePageState extends State<PlatformAdaptingHomePage> {
             label: SongsTab.title,
             icon: SongsTab.iosIcon,
           ),
-          BottomNavigationBarItem(label: NewsTab.title, icon: NewsTab.iosIcon),
+          BottomNavigationBarItem(
+            label: NewsTab.title,
+            icon: NewsTab.iosIcon,
+          ),
           BottomNavigationBarItem(
             label: ProfileTab.title,
             icon: ProfileTab.iosIcon,
@@ -168,7 +172,9 @@ class _AndroidDrawer extends StatelessWidget {
               Navigator.pop(context);
               Navigator.push<void>(
                 context,
-                MaterialPageRoute(builder: (context) => const ProfileTab()),
+                MaterialPageRoute(
+                  builder: (context) => const ProfileTab(),
+                ),
               );
             },
           ),
@@ -184,7 +190,9 @@ class _AndroidDrawer extends StatelessWidget {
               Navigator.pop(context);
               Navigator.push<void>(
                 context,
-                MaterialPageRoute(builder: (context) => const SettingsTab()),
+                MaterialPageRoute(
+                  builder: (context) => const SettingsTab(),
+                ),
               );
             },
           ),