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/search_form/widgets/search_form_guests.dart

@@ -75,14 +75,12 @@ class _QuantitySelector extends StatelessWidget {
           ),
           ListenableBuilder(
             listenable: viewModel,
-            builder:
-                (context, _) => Text(
-                  viewModel.guests.toString(),
-                  style:
-                      viewModel.guests == 0
-                          ? Theme.of(context).inputDecorationTheme.hintStyle
-                          : Theme.of(context).textTheme.bodyMedium,
-                ),
+            builder: (context, _) => Text(
+              viewModel.guests.toString(),
+              style: viewModel.guests == 0
+                  ? Theme.of(context).inputDecorationTheme.hintStyle
+                  : Theme.of(context).textTheme.bodyMedium,
+            ),
           ),
           InkWell(
             key: const ValueKey(addGuestsKey),

compass_app/app/lib/ui/search_form/widgets/search_form_submit.dart

@@ -65,10 +65,9 @@ class _SearchFormSubmitState extends State<SearchFormSubmit> {
         builder: (context, child) {
           return FilledButton(
             key: const ValueKey(searchFormSubmitButtonKey),
-            onPressed:
-                widget.viewModel.valid
-                    ? widget.viewModel.updateItineraryConfig.execute
-                    : null,
+            onPressed: widget.viewModel.valid
+                ? widget.viewModel.updateItineraryConfig.execute
+                : null,
             child: child,
           );
         },