chore: adopt Dart 3.9 toolchain — honest floor + tall-style reformat (T-353)

Raise the declared minimums in pubspec.yaml to what our deps already
require: Flutter >=3.35.0 / Dart >=3.9.0 (was 3.19.0 / 3.5.0). alchemist
0.12 needs Flutter 3.32; Dart 3.9 first ships in Flutter 3.35, so 3.35 is
the binding floor. Pin the exact build toolchain in .fvmrc (Flutter
3.44.1).

Moving to the Dart 3.9 language level switches `dart format` to the new
"tall" style and enables two new lints. This commit is the resulting
mechanical churn, isolated from any behaviour change:
  - whole-tree `dart format` reformat (tall style)
  - `dart fix` for unnecessary_underscores + use_null_aware_elements

No runtime behaviour change; `make test` green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/builtin/menubar/src/about_dialog.dart

@@ -66,7 +66,9 @@ class _Kv extends StatelessWidget {
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
           SizedBox(width: 90, child: ClideText(label, fontSize: 13, color: tokens.globalTextMuted)),
-          Expanded(child: ClideText(value, fontSize: 13, fontFamily: clideMonoFamily, maxLines: 1, overflow: TextOverflow.ellipsis)),
+          Expanded(
+            child: ClideText(value, fontSize: 13, fontFamily: clideMonoFamily, maxLines: 1, overflow: TextOverflow.ellipsis),
+          ),
         ],
       ),
     );
@@ -89,7 +91,10 @@ class _Licenses extends StatelessWidget {
         final deps = snap.data!.dependencies;
         return Container(
           constraints: const BoxConstraints(maxHeight: 260),
-          decoration: BoxDecoration(border: Border.all(color: tokens.globalBorder), borderRadius: BorderRadius.circular(4)),
+          decoration: BoxDecoration(
+            border: Border.all(color: tokens.globalBorder),
+            borderRadius: BorderRadius.circular(4),
+          ),
           child: ListView.builder(
             shrinkWrap: true,
             padding: const EdgeInsets.symmetric(vertical: 4),

lib/builtin/menubar/src/extension.dart

@@ -26,67 +26,77 @@ class MenuBarExtension extends ClideExtension {
 
   @override
   List<ContributionPoint> get contributions => [
-        CommandContribution(
-          id: 'file.openFolder',
-          command: 'file.openFolder',
-          title: 'File: Open Folder…',
-          run: (_) async {
-            await _file.openFolder();
-            return IpcResponse.ok(id: '', data: const {});
-          },
-        ),
-        CommandContribution(
-          id: 'file.newWindow',
-          command: 'file.newWindow',
-          title: 'File: New Window',
-          run: (_) async {
-            _file.newWindow();
-            return IpcResponse.ok(id: '', data: const {});
-          },
-        ),
-        CommandContribution(
-          id: 'file.closeWorkspace',
-          command: 'file.closeWorkspace',
-          title: 'File: Close Project',
-          run: (_) async {
-            _file.closeWorkspace();
-            return IpcResponse.ok(id: '', data: const {});
-          },
-        ),
-        CommandContribution(
-          id: 'help.about',
-          command: 'help.about',
-          title: 'Help: About clide',
-          run: (_) async {
-            services.dialog.show<Object>((ctx, dismiss) => AboutDialog(onDismiss: () => dismiss()));
-            return IpcResponse.ok(id: '', data: const {});
-          },
-        ),
-      ];
+    CommandContribution(
+      id: 'file.openFolder',
+      command: 'file.openFolder',
+      title: 'File: Open Folder…',
+      run: (_) async {
+        await _file.openFolder();
+        return IpcResponse.ok(id: '', data: const {});
+      },
+    ),
+    CommandContribution(
+      id: 'file.newWindow',
+      command: 'file.newWindow',
+      title: 'File: New Window',
+      run: (_) async {
+        _file.newWindow();
+        return IpcResponse.ok(id: '', data: const {});
+      },
+    ),
+    CommandContribution(
+      id: 'file.closeWorkspace',
+      command: 'file.closeWorkspace',
+      title: 'File: Close Project',
+      run: (_) async {
+        _file.closeWorkspace();
+        return IpcResponse.ok(id: '', data: const {});
+      },
+    ),
+    CommandContribution(
+      id: 'help.about',
+      command: 'help.about',
+      title: 'Help: About clide',
+      run: (_) async {
+        services.dialog.show<Object>((ctx, dismiss) => AboutDialog(onDismiss: () => dismiss()));
+        return IpcResponse.ok(id: '', data: const {});
+      },
+    ),
+  ];
 }
 
 /// The curated File / View / Help tree (T-48). View ends with a `view.*`
 /// auto-fill so newly-registered view commands surface without edits here.
 List<TopMenu> buildClideMenuTree() => [
-      TopMenu(title: 'File', mnemonic: 0, nodes: [
-        const MenuCommandItem('file.openFolder', fallbackTitle: 'Open Folder…'),
-        const MenuCommandItem('file.newWindow', fallbackTitle: 'New Window'),
-        const MenuSeparator(),
-        MenuCommandItem('file.closeWorkspace', fallbackTitle: 'Close Project', enabledWhen: (s) => s.project.isOpen),
-      ]),
-      TopMenu(title: 'View', mnemonic: 0, nodes: const [
-        MenuCommandItem('view.zoomIn'),
-        MenuCommandItem('view.zoomOut'),
-        MenuCommandItem('view.zoomReset'),
-        MenuSeparator(),
-        MenuCommandItem('sidebar.collapse'),
-        MenuCommandItem('context.collapse'),
-        MenuCommandItem('dock.toggle'),
-        MenuCommandItem('panel.focusMode'),
-        MenuSeparator(),
-        MenuAutoFill('view.'),
-      ]),
-      TopMenu(title: 'Help', mnemonic: 0, nodes: const [
-        MenuCommandItem('help.about', fallbackTitle: 'About clide'),
-      ]),
-    ];
+  TopMenu(
+    title: 'File',
+    mnemonic: 0,
+    nodes: [
+      const MenuCommandItem('file.openFolder', fallbackTitle: 'Open Folder…'),
+      const MenuCommandItem('file.newWindow', fallbackTitle: 'New Window'),
+      const MenuSeparator(),
+      MenuCommandItem('file.closeWorkspace', fallbackTitle: 'Close Project', enabledWhen: (s) => s.project.isOpen),
+    ],
+  ),
+  TopMenu(
+    title: 'View',
+    mnemonic: 0,
+    nodes: const [
+      MenuCommandItem('view.zoomIn'),
+      MenuCommandItem('view.zoomOut'),
+      MenuCommandItem('view.zoomReset'),
+      MenuSeparator(),
+      MenuCommandItem('sidebar.collapse'),
+      MenuCommandItem('context.collapse'),
+      MenuCommandItem('dock.toggle'),
+      MenuCommandItem('panel.focusMode'),
+      MenuSeparator(),
+      MenuAutoFill('view.'),
+    ],
+  ),
+  TopMenu(
+    title: 'Help',
+    mnemonic: 0,
+    nodes: const [MenuCommandItem('help.about', fallbackTitle: 'About clide')],
+  ),
+];

lib/builtin/menubar/src/file_actions.dart

@@ -143,10 +143,7 @@ class _OpenFolderDialogState extends State<OpenFolderDialog> {
               onSubmitted: (_) => unawaited(_submit()),
             ),
           ),
-          if (_error != null) ...[
-            const SizedBox(height: 8),
-            ClideText(_error!, color: tokens.statusError, fontSize: 12),
-          ],
+          if (_error != null) ...[const SizedBox(height: 8), ClideText(_error!, color: tokens.statusError, fontSize: 12)],
           const SizedBox(height: 16),
           Row(
             mainAxisAlignment: MainAxisAlignment.end,
@@ -188,17 +185,11 @@ class NotARepoDialog extends StatelessWidget {
           const SizedBox(height: 8),
           ClideText(path, muted: true, fontSize: 13),
           const SizedBox(height: 8),
-          const ClideText(
-            'A clide project root requires a git repository.',
-            muted: true,
-            fontSize: 13,
-          ),
+          const ClideText('A clide project root requires a git repository.', muted: true, fontSize: 13),
           const SizedBox(height: 16),
           Row(
             mainAxisAlignment: MainAxisAlignment.end,
-            children: [
-              ClideButton(label: 'OK', onPressed: () => onDismiss()),
-            ],
+            children: [ClideButton(label: 'OK', onPressed: () => onDismiss())],
           ),
         ],
       ),

lib/builtin/menubar/src/menu_bar.dart

@@ -72,18 +72,11 @@ class MenuBar extends StatelessWidget {
     return ListenableBuilder(
       listenable: Listenable.merge([controller, kernel.commands, kernel.project]),
       builder: (ctx, _) {
-        final menus = resolveMenus(
-          buildClideMenuTree(),
-          kernel.commands,
-          kernel,
-          bindingLabel: (id) => keymapBindingLabel(kernel.keymap, id),
-        );
+        final menus = resolveMenus(buildClideMenuTree(), kernel.commands, kernel, bindingLabel: (id) => keymapBindingLabel(kernel.keymap, id));
         controller.setMnemonics([for (final m in menus) m.title[m.mnemonic].toLowerCase()]);
         return Row(
           mainAxisSize: MainAxisSize.min,
-          children: [
-            for (var i = 0; i < menus.length; i++) _TopMenuButton(index: i, menu: menus[i], controller: controller, kernel: kernel),
-          ],
+          children: [for (var i = 0; i < menus.length; i++) _TopMenuButton(index: i, menu: menus[i], controller: controller, kernel: kernel)],
         );
       },
     );
@@ -189,11 +182,7 @@ class _TopMenuButtonState extends State<_TopMenuButton> {
             alignment: Alignment.center,
             padding: const EdgeInsets.symmetric(horizontal: clideInsetStandard),
             color: open || hovered ? tokens.listItemHoverBackground : null,
-            child: ClideText(
-              widget.menu.title,
-              fontSize: 12,
-              color: open || hovered ? tokens.globalForeground : tokens.chromeForeground,
-            ),
+            child: ClideText(widget.menu.title, fontSize: 12, color: open || hovered ? tokens.globalForeground : tokens.chromeForeground),
           ),
         ),
       ),

lib/builtin/menubar/src/menu_model.dart

@@ -108,12 +108,7 @@ String? keymapBindingLabel(KeymapService keymap, String commandId) {
 /// menus. [bindingLabel] supplies the keybinding string for a command id
 /// (typically [keymapBindingLabel] bound to the keymap); when it returns null
 /// the command's own `defaultBinding` is used as a fallback.
-List<ResolvedMenu> resolveMenus(
-  List<TopMenu> tree,
-  CommandRegistry registry,
-  KernelServices services, {
-  String? Function(String commandId)? bindingLabel,
-}) {
+List<ResolvedMenu> resolveMenus(List<TopMenu> tree, CommandRegistry registry, KernelServices services, {String? Function(String commandId)? bindingLabel}) {
   final placed = <String>{
     for (final m in tree)
       for (final n in m.nodes)
@@ -140,12 +135,10 @@ List<ResolvedMenu> resolveMenus(
   }
 
   List<ResolvedNode> expand(MenuNode n) => switch (n) {
-        MenuCommandItem() => [resolveItem(n)],
-        MenuSeparator() => const [ResolvedSeparator()],
-        MenuAutoFill(:final prefix) => [
-            for (final c in _autoFill(registry, prefix, placed)) resolveItem(MenuCommandItem(c.command)),
-          ],
-      };
+    MenuCommandItem() => [resolveItem(n)],
+    MenuSeparator() => const [ResolvedSeparator()],
+    MenuAutoFill(:final prefix) => [for (final c in _autoFill(registry, prefix, placed)) resolveItem(MenuCommandItem(c.command))],
+  };
 
   return [
     for (final m in tree) ResolvedMenu(title: m.title, mnemonic: m.mnemonic, items: [for (final n in m.nodes) ...expand(n)]),