seekable: prioritize dragging playhead over workarea

app/widget/timeruler/seekablewidget.h

@@ -125,6 +125,8 @@ private:
 
   bool FindResizeHandle(QMouseEvent *event);
 
+  void ClearResizeHandle();
+
   void DragResizeHandle(const QPointF &scene_pos);
 
   void CommitResizeHandle();
@@ -153,6 +155,8 @@ private:
 
   bool marker_editing_enabled_;
 
+  QPolygon last_playhead_shape_;
+
 private slots:
   void SetMarkerColor(int c);