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 `///`).

pedometer/example/lib/main.dart

@@ -65,20 +65,19 @@ class _HomeState extends State<Home> {
   Widget build(BuildContext context) {
     final textTheme = Theme.of(context).textTheme;
 
-    final barGroups =
-        hourlySteps
-            .map(
-              (e) => BarChartGroupData(
-                x: int.parse(e.startHour),
-                barRods: [
-                  BarChartRodData(
-                    color: Colors.blue[900],
-                    toY: e.steps.toDouble() / 100,
-                  ),
-                ],
+    final barGroups = hourlySteps
+        .map(
+          (e) => BarChartGroupData(
+            x: int.parse(e.startHour),
+            barRods: [
+              BarChartRodData(
+                color: Colors.blue[900],
+                toY: e.steps.toDouble() / 100,
               ),
-            )
-            .toList();
+            ],
+          ),
+        )
+        .toList();
 
     return Scaffold(
       body: Stack(
@@ -99,14 +98,14 @@ class _HomeState extends State<Home> {
                 children: [
                   lastUpdated != null
                       ? Padding(
-                        padding: const EdgeInsets.symmetric(vertical: 50.0),
-                        child: Text(
-                          DateFormat.yMMMMd('en_US').format(lastUpdated!),
-                          style: textTheme.titleLarge!.copyWith(
-                            color: Colors.blue[900],
+                          padding: const EdgeInsets.symmetric(vertical: 50.0),
+                          child: Text(
+                            DateFormat.yMMMMd('en_US').format(lastUpdated!),
+                            style: textTheme.titleLarge!.copyWith(
+                              color: Colors.blue[900],
+                            ),
                           ),
-                        ),
-                      )
+                        )
                       : const SizedBox(height: 0),
                   Text(
                     hourlySteps.fold(0, (t, e) => t + e.steps).toString(),