Replace Refresh with Invalidate in DrawPanelPaint

Modified DrawPanelPaint to use _DrawPanel.Invalidate() instead of _DrawPanel.Refresh(). This change aims to improve the repainting process by invalidating the panel, which sends a paint message to the panel rather than immediately refreshing it.

RdlDesign/DesignCtl.cs

@@ -1104,7 +1104,7 @@ private async void DrawPanelPaint(object sender, System.Windows.Forms.PaintEvent
                 await Internal_DrawPanelPaint();
                 doGraphicsDraw = true;
                 // HACK: async shenanigans, force a repaint where e.Graphics is still valid
-                _DrawPanel.Refresh();       
+                _DrawPanel.Invalidate();       
             }
         }