remove MicrotabLeadOut — redundant with normal tabs

MicrotabLeadOut was an unimplemented stub (Generate returned empty list)
that duplicated tab functionality. Existing saved configs with "Microtab"
selected will gracefully fall back to NoLeadOut.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -1,16 +0,0 @@
-using OpenNest.Geometry;
-using System.Collections.Generic;
-
-namespace OpenNest.CNC.CuttingStrategy
-{
-    public class MicrotabLeadOut : LeadOut
-    {
-        public double GapSize { get; set; } = 0.03;
-
-        public override List<ICode> Generate(Vector contourEndPoint, double contourNormalAngle,
-            RotationType winding = RotationType.CW)
-        {
-            return new List<ICode>();
-        }
-    }
-}