refactor(ui): simplify create task advanced disclosure

ui/flutter/lib/features/tasks/presentation/pages/create_task_window_page.dart

@@ -41,6 +41,7 @@ import '../../application/pending_download.dart';
 import '../../application/task_list_navigation.dart';
 import '../widgets/history_search_field.dart';
 import '../widgets/create_task_action_buttons.dart';
+import '../widgets/create_task_advanced_toggle.dart';
 import '../widgets/resolve_download_dialog.dart';
 
 class CreateTaskWindowPage extends ConsumerStatefulWidget {
@@ -560,20 +561,11 @@ class _CreateTaskWindowPageState extends ConsumerState<CreateTaskWindowPage> {
                     ),
                     const SizedBox(height: 20),
                     Align(
-                      alignment: Alignment.centerLeft,
-                      child: GestureDetector(
-                        onTap: _toggleAdvanced,
-                        child: Row(
-                          mainAxisSize: MainAxisSize.min,
-                          children: [
-                            Text(
-                              context.l10n.advanced,
-                              style: TextStyle(color: palette.textPrimary, fontSize: 14, fontWeight: FontWeight.w600),
-                            ),
-                            const SizedBox(width: 8),
-                            _TripleChevronIcon(expanded: _showAdvanced, color: palette.textSecondary),
-                          ],
-                        ),
+                      alignment: AlignmentDirectional.centerStart,
+                      child: CreateTaskAdvancedToggle(
+                        key: const ValueKey('create-task-advanced-toggle'),
+                        expanded: _showAdvanced,
+                        onPressed: _toggleAdvanced,
                       ),
                     ),
                     AnimatedCrossFade(
@@ -1933,30 +1925,6 @@ class _MiniInputAction extends StatelessWidget {
   }
 }
 
-class _TripleChevronIcon extends StatelessWidget {
-  const _TripleChevronIcon({required this.expanded, required this.color});
-
-  final bool expanded;
-  final Color color;
-
-  @override
-  Widget build(BuildContext context) {
-    final icon = expanded ? Icons.expand_less : Icons.expand_more;
-    return SizedBox(
-      width: 14,
-      height: 18,
-      child: Stack(
-        clipBehavior: Clip.none,
-        children: [
-          Positioned(top: 0, left: 0, child: Icon(icon, size: 14, color: color)),
-          Positioned(top: 4, left: 0, child: Icon(icon, size: 14, color: color)),
-          Positioned(top: 8, left: 0, child: Icon(icon, size: 14, color: color)),
-        ],
-      ),
-    );
-  }
-}
-
 class _SegmentButton extends StatelessWidget {
   const _SegmentButton({required this.label, required this.active, required this.onTap});
 

ui/flutter/lib/features/tasks/presentation/widgets/create_task_advanced_toggle.dart

@@ -0,0 +1,49 @@
+import 'package:shadcn_flutter/shadcn_flutter.dart';
+
+import '../../../../l10n/l10n.dart';
+import '../../../../shared/theme/app_design_tokens.dart';
+import '../../../../shared/theme/app_palette.dart';
+
+/// A quiet disclosure control with the same keyboard behavior as other buttons.
+class CreateTaskAdvancedToggle extends StatelessWidget {
+  const CreateTaskAdvancedToggle({super.key, required this.expanded, required this.onPressed});
+
+  final bool expanded;
+  final VoidCallback onPressed;
+
+  @override
+  Widget build(BuildContext context) {
+    final palette = AppPalette.of(context);
+    final reduceMotion = MediaQuery.disableAnimationsOf(context);
+    return Semantics(
+      expanded: expanded,
+      child: ButtonStyleOverride.inherit(
+        padding: (context, states, value) => const EdgeInsets.symmetric(vertical: AppDesignTokens.space12),
+        child: GhostButton(
+          onPressed: onPressed,
+          child: ConstrainedBox(
+            constraints: const BoxConstraints(minHeight: 20),
+            child: Row(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                Flexible(
+                  child: Text(
+                    context.l10n.advanced,
+                    style: TextStyle(color: palette.textPrimary, fontSize: 14, fontWeight: FontWeight.w600),
+                  ),
+                ),
+                const SizedBox(width: AppDesignTokens.space8),
+                AnimatedRotation(
+                  turns: expanded ? 0.5 : 0,
+                  duration: reduceMotion ? Duration.zero : const Duration(milliseconds: 180),
+                  curve: Curves.easeOutCubic,
+                  child: Icon(Icons.keyboard_arrow_down, size: 16, color: palette.textSecondary),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}