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/Controls/PlateView.cs

@@ -127,7 +127,8 @@ namespace OpenNest.Controls
             foreach (var part in plate.Parts)
                 parts.Add(LayoutPart.Create(part, this));
 
-            SetAction(typeof(ActionSelect));
+            if (currentAction == null || !currentAction.SurvivesPlateChange)
+                SetAction(typeof(ActionSelect));
         }
 
         public string Status