refactor(cutting): move owned program copies into Core

Core's commit freshness check needs the same lossless program copy the
planner uses at capture. Move it unchanged apart from its namespace.

OpenNest.Core/CNC/CuttingPlanning/OwnedProgramCopy.cs

@@ -1,9 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Threading;
-using OpenNest.CNC;
 
-namespace OpenNest.Engine.CuttingPlanning;
+namespace OpenNest.CNC.CuttingPlanning;
 
 /// <summary>Lossless owned copies at the cutting-plan boundary, not a general Clone change.</summary>
 internal static class OwnedProgramCopy