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/basic_text_field.dart

@@ -89,7 +89,9 @@ class _BasicTextFieldState extends State<BasicTextField> {
     TextSelection selection,
     SelectionChangedCause? cause,
   ) {
-    final bool willShowSelectionHandles = _shouldShowSelectionHandles(cause);
+    final bool willShowSelectionHandles = _shouldShowSelectionHandles(
+      cause,
+    );
     if (willShowSelectionHandles != _showSelectionHandles) {
       setState(() {
         _showSelectionHandles = willShowSelectionHandles;
@@ -98,16 +100,15 @@ class _BasicTextFieldState extends State<BasicTextField> {
   }
 
   void _onDragUpdate(DragUpdateDetails details) {
-    final Offset startOffset =
-        _renderEditable.maxLines == 1
-            ? Offset(
-              _renderEditable.offset.pixels - _dragStartViewportOffset,
-              0.0,
-            )
-            : Offset(
-              0.0,
-              _renderEditable.offset.pixels - _dragStartViewportOffset,
-            );
+    final Offset startOffset = _renderEditable.maxLines == 1
+        ? Offset(
+            _renderEditable.offset.pixels - _dragStartViewportOffset,
+            0.0,
+          )
+        : Offset(
+            0.0,
+            _renderEditable.offset.pixels - _dragStartViewportOffset,
+          );
 
     _renderEditable.selectPositionAt(
       from: _startDetails.globalPosition - startOffset,
@@ -134,7 +135,8 @@ class _BasicTextFieldState extends State<BasicTextField> {
         _textSelectionControls = cupertinoTextSelectionHandleControls;
       case TargetPlatform.macOS:
         // ignore: deprecated_member_use
-        _textSelectionControls = cupertinoDesktopTextSelectionHandleControls;
+        _textSelectionControls =
+            cupertinoDesktopTextSelectionHandleControls;
       case TargetPlatform.android:
       case TargetPlatform.fuchsia:
         // ignore: deprecated_member_use
@@ -151,7 +153,8 @@ class _BasicTextFieldState extends State<BasicTextField> {
       child: GestureDetector(
         behavior: HitTestBehavior.translucent,
         onPanStart: (dragStartDetails) => _onDragStart(dragStartDetails),
-        onPanUpdate: (dragUpdateDetails) => _onDragUpdate(dragUpdateDetails),
+        onPanUpdate: (dragUpdateDetails) =>
+            _onDragUpdate(dragUpdateDetails),
         onSecondaryTapDown: (secondaryTapDownDetails) {
           _renderEditable.selectWordsInRange(
             from: secondaryTapDownDetails.globalPosition,
@@ -190,12 +193,12 @@ class _BasicTextFieldState extends State<BasicTextField> {
               );
           }
         },
-        onLongPressEnd:
-            (longPressEndDetails) => _textInputClient!.showToolbar(),
-        onHorizontalDragStart:
-            (dragStartDetails) => _onDragStart(dragStartDetails),
-        onHorizontalDragUpdate:
-            (dragUpdateDetails) => _onDragUpdate(dragUpdateDetails),
+        onLongPressEnd: (longPressEndDetails) =>
+            _textInputClient!.showToolbar(),
+        onHorizontalDragStart: (dragStartDetails) =>
+            _onDragStart(dragStartDetails),
+        onHorizontalDragUpdate: (dragUpdateDetails) =>
+            _onDragUpdate(dragUpdateDetails),
         child: SizedBox(
           height: double.infinity,
           width: MediaQuery.of(context).size.width,