refactor(ui): simplify create task advanced disclosure

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),
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}