Enhance drag functionality to directly use Scrollable as dragStart in Act class

Author: trejdych

lib/src/act/act.dart

@@ -266,8 +266,11 @@ class Act {
 
     // Take the closest Scrollable above the dragStart widget. This is the
     // widget which makes a widget scrollable. It must always exist.
-    final WidgetSelector<Scrollable> scrollable =
-        spot<Scrollable>().withChild(dragStart).last();
+    // If dragStart is already a Scrollable, use it directly instead of searching for a parent.
+    final WidgetSelector<Scrollable> scrollable = switch (dragStart) {
+      final WidgetSelector<Scrollable> s => s,
+      _ => spot<Scrollable>().withChild(dragStart).last(),
+    };
 
     // Save the 'Element' of the currently targeted Scrollable.
     // This ensures that—even if multiple scrollables exist or the

test/act/act_drag_test.dart

@@ -119,6 +119,31 @@ void dragTests() {
         await act.tap(secondItem);
       },
     );
+
+    testWidgets(
+      'Finds widget in vertical ListView after dragging when dragStart is a Scrollable',
+      (tester) async {
+        await tester.pumpWidget(
+          const DragUntilVisibleSingleDirectionTestWidget(
+            axis: Axis.vertical,
+            ignorePointerAtIndices: [0, 1, 2, 3, 4, 5, 6, 7, 8],
+          ),
+        );
+
+        final firstItem = spot<DragUntilVisibleSingleDirectionTestWidget>()
+            .spot<Scrollable>()
+            .last()
+          ..existsOnce();
+        final secondItem = spotText('Item at index: 27', exact: true)
+          ..doesNotExist();
+        await act.dragUntilVisible(
+          dragStart: firstItem,
+          dragTarget: secondItem,
+          maxIteration: 30,
+        );
+        secondItem.existsOnce();
+      },
+    );
   });
 
   group('Horizontal Drag', () {