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_channels/lib/src/add_pet_details.dart

@@ -31,7 +31,10 @@ class _AddPetDetailsState extends State<AddPetDetails> {
             icon: const Icon(Icons.add),
             onPressed: () {
               PetListMessageChannel.addPetDetails(
-                PetDetails(petType: petType, breed: breedTextController.text),
+                PetDetails(
+                  petType: petType,
+                  breed: breedTextController.text,
+                ),
               );
 
               context.pop();
@@ -61,8 +64,14 @@ class _AddPetDetailsState extends State<AddPetDetails> {
                 ),
               ),
               const SizedBox(height: 8),
-              RadioListTile<String>(title: const Text('Dog'), value: 'Dog'),
-              RadioListTile<String>(title: const Text('Cat'), value: 'Cat'),
+              RadioListTile<String>(
+                title: const Text('Dog'),
+                value: 'Dog',
+              ),
+              RadioListTile<String>(
+                title: const Text('Cat'),
+                value: 'Cat',
+              ),
             ],
           ),
         ),