fix(player): 预热直出并与视频统一封面布局

lib/pages/player/widgets/scrub_preview_card.dart

@@ -256,26 +256,37 @@ class SpriteCropPreview extends StatelessWidget {
     super.key,
     required this.image,
     required this.sourceRect,
+    this.fit = BoxFit.cover,
   });
 
   final ui.Image image;
   final ui.Rect sourceRect;
+  final BoxFit fit;
 
   @override
   Widget build(BuildContext context) => CustomPaint(
-    painter: _SpriteCropPainter(image: image, sourceRect: sourceRect),
+    painter: _SpriteCropPainter(
+      image: image,
+      sourceRect: sourceRect,
+      fit: fit,
+    ),
   );
 }
 
 class _SpriteCropPainter extends CustomPainter {
-  const _SpriteCropPainter({required this.image, required this.sourceRect});
+  const _SpriteCropPainter({
+    required this.image,
+    required this.sourceRect,
+    required this.fit,
+  });
 
   final ui.Image image;
   final ui.Rect sourceRect;
+  final BoxFit fit;
 
   @override
   void paint(Canvas canvas, Size size) {
-    final fitted = applyBoxFit(BoxFit.cover, sourceRect.size, size);
+    final fitted = applyBoxFit(fit, sourceRect.size, size);
     final sourceOffset = Alignment.center.inscribe(
       fitted.source,
       Offset.zero & sourceRect.size,
@@ -302,7 +313,9 @@ class _SpriteCropPainter extends CustomPainter {
 
   @override
   bool shouldRepaint(covariant _SpriteCropPainter oldDelegate) =>
-      oldDelegate.image != image || oldDelegate.sourceRect != sourceRect;
+      oldDelegate.image != image ||
+      oldDelegate.sourceRect != sourceRect ||
+      oldDelegate.fit != fit;
 }
 
 String _format(Duration value) {