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 `///`).

code_sharing/shared/lib/src/models.freezed.dart

@@ -52,11 +52,10 @@ class _$IncrementCopyWithImpl<$Res, $Val extends Increment>
   $Res call({Object? by = null}) {
     return _then(
       _value.copyWith(
-            by:
-                null == by
-                    ? _value.by
-                    : by // ignore: cast_nullable_to_non_nullable
-                        as int,
+            by: null == by
+                ? _value.by
+                : by // ignore: cast_nullable_to_non_nullable
+                      as int,
           )
           as $Val,
     );
@@ -89,11 +88,10 @@ class __$$IncrementImplCopyWithImpl<$Res>
   $Res call({Object? by = null}) {
     return _then(
       _$IncrementImpl(
-        by:
-            null == by
-                ? _value.by
-                : by // ignore: cast_nullable_to_non_nullable
-                    as int,
+        by: null == by
+            ? _value.by
+            : by // ignore: cast_nullable_to_non_nullable
+                  as int,
       ),
     );
   }
@@ -189,11 +187,10 @@ class _$CountCopyWithImpl<$Res, $Val extends Count>
   $Res call({Object? value = null}) {
     return _then(
       _value.copyWith(
-            value:
-                null == value
-                    ? _value.value
-                    : value // ignore: cast_nullable_to_non_nullable
-                        as int,
+            value: null == value
+                ? _value.value
+                : value // ignore: cast_nullable_to_non_nullable
+                      as int,
           )
           as $Val,
     );
@@ -228,7 +225,7 @@ class __$$CountImplCopyWithImpl<$Res>
         null == value
             ? _value.value
             : value // ignore: cast_nullable_to_non_nullable
-                as int,
+                  as int,
       ),
     );
   }

code_sharing/shared/pubspec.yaml

@@ -1,15 +1,18 @@
 name: shared
 description: Common data models required by our client and server
 version: 1.0.0
+resolution: workspace
 
 environment:
-  sdk: ^3.7.0-0
+  sdk: ^3.9.0-0
 
 dependencies:
   freezed_annotation: ">=2.1.0 <4.0.0"
   json_annotation: ^4.7.0
 
 dev_dependencies:
+  analysis_defaults:
+    path: ../../analysis_defaults
   build_runner: ^2.2.1
   freezed: ">=2.1.1 <4.0.0"
   json_serializable: ^6.4.0