feat: add LeadOut hierarchy (5 classes)

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

OpenNest.Core/CNC/CuttingStrategy/LeadOuts/LeadOut.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+using OpenNest.Geometry;
+
+namespace OpenNest.CNC.CuttingStrategy
+{
+    public abstract class LeadOut
+    {
+        public abstract List<ICode> Generate(Vector contourEndPoint, double contourNormalAngle,
+            RotationType winding = RotationType.CW);
+    }
+}