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 `///`).

compass_app/app/lib/ui/activities/widgets/activities_screen.dart

@@ -71,10 +71,9 @@ class _ActivitiesScreenState extends State<ActivitiesScreen> {
                   Expanded(
                     child: Center(
                       child: ErrorIndicator(
-                        title:
-                            AppLocalization.of(
-                              context,
-                            ).errorWhileLoadingActivities,
+                        title: AppLocalization.of(
+                          context,
+                        ).errorWhileLoadingActivities,
                         label: AppLocalization.of(context).tryAgain,
                         onPressed: widget.viewModel.loadActivities.execute,
                       ),
@@ -171,10 +170,9 @@ class _BottomArea extends StatelessWidget {
               ),
               FilledButton(
                 key: const Key(confirmButtonKey),
-                onPressed:
-                    viewModel.selectedActivities.isNotEmpty
-                        ? viewModel.saveActivities.execute
-                        : null,
+                onPressed: viewModel.selectedActivities.isNotEmpty
+                    ? viewModel.saveActivities.execute
+                    : null,
                 child: Text(AppLocalization.of(context).confirm),
               ),
             ],