fix(player): 持久化竖滑播放画面层

test/player/player_fullscreen_test.dart

@@ -55,6 +55,19 @@ void main() {
       pageViews.where((pageView) => pageView.scrollDirection == Axis.vertical),
       hasLength(1),
     );
+    expect(find.byKey(const Key('player-render-stack')), findsOneWidget);
+    final renderStackPageAncestors = tester.widgetList<PageView>(
+      find.ancestor(
+        of: find.byKey(const Key('player-render-stack')),
+        matching: find.byType(PageView),
+      ),
+    );
+    expect(
+      renderStackPageAncestors.where(
+        (pageView) => pageView.scrollDirection == Axis.vertical,
+      ),
+      isEmpty,
+    );
     expect(tester.takeException(), isNull);
   });