fix: preserve ActionClone across plate switches

SetPlate unconditionally reset the action to ActionSelect, clearing
the clone pattern when switching plates. Add SurvivesPlateChange
virtual property to Action base class so actions can opt in to
persisting across plate changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest/Actions/ActionClone.cs

@@ -98,6 +98,8 @@ namespace OpenNest.Actions
             plateView.Invalidate();
         }
 
+        public override bool SurvivesPlateChange => true;
+
         public override void DisconnectEvents()
         {
             plateView.KeyDown -= plateView_KeyDown;