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 `///`).

deeplink_store_example/lib/main.dart

@@ -33,14 +33,14 @@ class MyApp extends StatelessWidget {
         routes: [
           GoRoute(
             path: '/',
-            builder: (_, __) => const ProductList(),
+            builder: (_, _) => const ProductList(),
             routes: [
-              GoRoute(path: ':id', builder: (_, __) => const ProductDetails()),
+              GoRoute(path: ':id', builder: (_, _) => const ProductDetails()),
             ],
           ),
           GoRoute(
             path: '/category/:category',
-            builder: (_, __) => const ProductCategoryList(),
+            builder: (_, _) => const ProductCategoryList(),
           ),
         ],
       ),

deeplink_store_example/lib/product_category_list.dart

@@ -30,10 +30,9 @@ class ProductCategoryList extends StatelessWidget {
           value.toString().contains(state.pathParameters['category']!),
       orElse: () => Category.all,
     );
-    final List<Widget> children =
-        ProductsRepository.loadProducts(
-          category: category,
-        ).map<Widget>((Product p) => RowItem(product: p)).toList();
+    final List<Widget> children = ProductsRepository.loadProducts(
+      category: category,
+    ).map<Widget>((Product p) => RowItem(product: p)).toList();
     return Scaffold(
       backgroundColor: Styles.scaffoldBackground,
       body: CustomScrollView(

deeplink_store_example/lib/product_list.dart

@@ -23,10 +23,9 @@ class ProductList extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final List<Widget> children =
-        ProductsRepository.loadProducts()
-            .map<Widget>((Product p) => RowItem(product: p))
-            .toList();
+    final List<Widget> children = ProductsRepository.loadProducts()
+        .map<Widget>((Product p) => RowItem(product: p))
+        .toList();
     return Scaffold(
       backgroundColor: Styles.scaffoldBackground,
       body: CustomScrollView(