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 `///`).

simplistic_editor/lib/formatting_toolbar.dart

@@ -31,10 +31,9 @@ class FormattingToolbar extends StatelessWidget {
                 ToggleButtonsState.underline,
               ),
             ],
-            onPressed:
-                (index) => AppStateWidget.of(
-                  context,
-                ).updateToggleButtonsStateOnButtonPressed(index),
+            onPressed: (index) => AppStateWidget.of(
+              context,
+            ).updateToggleButtonsStateOnButtonPressed(index),
             children: const [
               Icon(Icons.format_bold),
               Icon(Icons.format_italic),