feat: add etch mark entities from bend lines to CNC program pipeline

Etch marks for up bends are now real geometry entities on an ETCH layer
instead of being drawn dynamically. They flow through the full pipeline:
entities → FilterPanel layers → ConvertGeometry (tagged as Scribe) →
post-processor sequencing before cut geometry.

Also includes ShapeProfile normalization (CW perimeter, CCW cutouts)
applied consistently across all import paths, and inward offset support
for cutout shapes in overlap/offset polygon calculations.

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

OpenNest.Engine/BestFit/PolygonHelper.cs

@@ -22,18 +22,11 @@ namespace OpenNest.Engine.BestFit
             if (perimeter == null)
                 return new PolygonExtractionResult(null, Vector.Zero);
 
-            // Inflate by half-spacing if spacing is non-zero.
-            // Detect winding direction to choose the correct outward offset side.
-            var outwardSide = OffsetSide.Right;
-            if (halfSpacing > 0)
-            {
-                var testPoly = perimeter.ToPolygon();
-                if (testPoly.Vertices.Count >= 3 && testPoly.RotationDirection() == RotationType.CW)
-                    outwardSide = OffsetSide.Left;
-            }
+            // Ensure CW winding for correct outward offset direction.
+            definedShape.NormalizeWinding();
 
             var inflated = halfSpacing > 0
-                ? (perimeter.OffsetEntity(halfSpacing, outwardSide) as Shape ?? perimeter)
+                ? (perimeter.OffsetOutward(halfSpacing) ?? perimeter)
                 : perimeter;
 
             // Convert to polygon with circumscribed arcs for tight nesting.