feat(app): 完善播放协议搜索与空状态

lib/pages/player/widgets/player_overlay.dart

@@ -220,11 +220,12 @@ class PlayerPlaybackOverlay extends StatelessWidget {
           ),
           if (data.boosting) _boostHint(),
           _bottomProgress(),
-          // 加速或拖动进度时只留进度条，避免挡住画面。
-          Offstage(
-            offstage: data.boosting || scrubbing,
-            child: _bottomActions(),
-          ),
+          // 加速时收起底栏。拖动进度时底栏只隐藏，占位保留，进度条不挪位。
+          scrubbing
+              ? IgnorePointer(
+                  child: Opacity(opacity: 0, child: _bottomActions()),
+                )
+              : Offstage(offstage: data.boosting, child: _bottomActions()),
         ],
       ),
     );