fix(player): 预热直出并与视频统一封面布局

test/player/player_opening_frame_test.dart

@@ -83,13 +83,9 @@ void main() {
     );
 
     expect(find.byKey(const Key('player-opening-poster')), findsOneWidget);
-    expect(
-      find.byKey(const Key('player-opening-poster-backdrop')),
-      findsOneWidget,
-    );
   });
 
-  testWidgets('should_constrain_poster_inside_native_vertical_frame', (
+  testWidgets('should_use_surface_fit_without_extra_frame_constraint', (
     tester,
   ) async {
     await tester.pumpWidget(
@@ -100,23 +96,23 @@ void main() {
       ),
     );
 
-    final stage = tester.widget<AspectRatio>(
-      find.byKey(const Key('player-opening-poster-stage')),
-    );
     final poster = tester.widget<RemoteImage>(
       find.byKey(const Key('player-opening-poster')),
     );
-    final backdrop = tester.widget<RemoteImage>(
-      find.byKey(const Key('player-opening-poster-backdrop')),
+
+    expect(poster.fit, BoxFit.cover);
+    expect(find.byType(AspectRatio), findsNothing);
+  });
+
+  test('should_forward_video_fit_to_opening_frame', () {
+    final frame = playerOpeningFrame(
+      null,
+      posterUrl: 'https://cdn.test/poster.jpg',
+      fit: BoxFit.contain,
     );
 
-    expect(stage.aspectRatio, closeTo(3 / 4, 0.001));
-    expect(poster.fit, BoxFit.cover);
-    expect(backdrop.fit, BoxFit.cover);
-    expect(
-      find.byKey(const Key('player-opening-poster-blur')),
-      findsOneWidget,
-    );
+    expect(frame, isA<PlayerOpeningFrame>());
+    expect((frame! as PlayerOpeningFrame).fit, BoxFit.contain);
   });
 
   testWidgets('should_reuse_decoded_sprite_when_parent_rebuilds', (