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 `///`).

context_menus/lib/reordered_buttons_page.dart

@@ -11,7 +11,8 @@ class ReorderedButtonsPage extends StatelessWidget {
 
   static const String route = 'reordered-buttons';
   static const String title = 'Reordered Buttons';
-  static const String subtitle = 'The usual buttons, but in a different order.';
+  static const String subtitle =
+      'The usual buttons, but in a different order.';
   static const String url = '$kCodeUrl/reordered_buttons_page.dart';
 
   final PlatformCallback onChangedPlatform;
@@ -61,19 +62,25 @@ class ReorderedButtonsPage extends StatelessWidget {
                       in editableTextState.contextMenuButtonItems) {
                     buttonItemsMap[buttonItem.type] = buttonItem;
                   }
-                  final List<ContextMenuButtonItem>
-                  reorderedButtonItems = <ContextMenuButtonItem>[
-                    if (buttonItemsMap.containsKey(
-                      ContextMenuButtonType.selectAll,
-                    ))
-                      buttonItemsMap[ContextMenuButtonType.selectAll]!,
-                    if (buttonItemsMap.containsKey(ContextMenuButtonType.paste))
-                      buttonItemsMap[ContextMenuButtonType.paste]!,
-                    if (buttonItemsMap.containsKey(ContextMenuButtonType.copy))
-                      buttonItemsMap[ContextMenuButtonType.copy]!,
-                    if (buttonItemsMap.containsKey(ContextMenuButtonType.cut))
-                      buttonItemsMap[ContextMenuButtonType.cut]!,
-                  ];
+                  final List<ContextMenuButtonItem> reorderedButtonItems =
+                      <ContextMenuButtonItem>[
+                        if (buttonItemsMap.containsKey(
+                          ContextMenuButtonType.selectAll,
+                        ))
+                          buttonItemsMap[ContextMenuButtonType.selectAll]!,
+                        if (buttonItemsMap.containsKey(
+                          ContextMenuButtonType.paste,
+                        ))
+                          buttonItemsMap[ContextMenuButtonType.paste]!,
+                        if (buttonItemsMap.containsKey(
+                          ContextMenuButtonType.copy,
+                        ))
+                          buttonItemsMap[ContextMenuButtonType.copy]!,
+                        if (buttonItemsMap.containsKey(
+                          ContextMenuButtonType.cut,
+                        ))
+                          buttonItemsMap[ContextMenuButtonType.cut]!,
+                      ];
                   return AdaptiveTextSelectionToolbar.buttonItems(
                     anchors: editableTextState.contextMenuAnchors,
                     buttonItems: reorderedButtonItems,