feat: add Tab hierarchy (4 classes)

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

OpenNest.Core/CNC/CuttingStrategy/Tabs/MachineTab.cs

@@ -0,0 +1,20 @@
+using System.Collections.Generic;
+using OpenNest.Geometry;
+
+namespace OpenNest.CNC.CuttingStrategy
+{
+    public class MachineTab : Tab
+    {
+        public int MachineTabId { get; set; }
+
+        public override List<ICode> Generate(
+            Vector tabStartPoint, Vector tabEndPoint, double contourNormalAngle,
+            RotationType winding = RotationType.CW)
+        {
+            return new List<ICode>
+            {
+                new RapidMove(tabEndPoint)
+            };
+        }
+    }
+}