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 `///`).

asset_transformation/analysis_options.yaml

@@ -1 +0,0 @@
-include: package:flutter_lints/flutter.yaml

asset_transformation/grayscale_transformer/bin/grayscale_transformer.dart

@@ -11,10 +11,9 @@ int main(List<String> arguments) {
   // the `--input` option and one for the `--output` option.
   // `--input` is the original asset file that this program should transform.
   // `--output` is where flutter expects the transformation output to be written to.
-  final parser =
-      ArgParser()
-        ..addOption(inputOptionName, mandatory: true, abbr: 'i')
-        ..addOption(outputOptionName, mandatory: true, abbr: 'o');
+  final parser = ArgParser()
+    ..addOption(inputOptionName, mandatory: true, abbr: 'i')
+    ..addOption(outputOptionName, mandatory: true, abbr: 'o');
 
   ArgResults argResults = parser.parse(arguments);
   final String inputFilePath = argResults[inputOptionName];

asset_transformation/grayscale_transformer/pubspec.yaml

@@ -3,7 +3,7 @@ description: A sample command-line application.
 version: 1.0.0
 
 environment:
-  sdk: ^3.7.0-0
+  sdk: ^3.9.0-0
 
 dependencies:
   args: ^2.4.2

asset_transformation/pubspec.yaml

@@ -2,9 +2,10 @@ name: asset_transformation
 description: "A new Flutter project."
 publish_to: 'none'
 version: 0.1.0
+resolution: workspace
 
 environment:
-  sdk: ^3.7.0-0
+  sdk: ^3.9.0-0
 
 dependencies:
   flutter:
@@ -12,9 +13,11 @@ dependencies:
   vector_graphics: ^1.1.11+1
 
 dev_dependencies:
+  analysis_defaults:
+    path: ../analysis_defaults
   flutter_test:
     sdk: flutter
-  flutter_lints: ^5.0.0
+  flutter_lints: ^6.0.0
   vector_graphics_compiler: ^1.1.11+1
   grayscale_transformer:
     path: ./grayscale_transformer