fix: resolve rendering issues when applying lead-ins to parts

Three issues caused incorrect rendering after lead-in application:
- Rapid move entities from ToGeometry() were included in ShapeProfile
  contour detection, turning traversal paths into cutting moves
- Program created with Mode.Incremental default made the absolute-to-
  incremental conversion a no-op, leaving coordinates unconverted
- AddProgramSplit didn't call StartFigure() at rapid moves, causing
  GraphicsPath to draw implicit connecting lines between contours
- Part.Rotation returned 0 from the new program instead of the actual
  rotation, displacing the sequence label on rotated parts

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

OpenNest.Core/CNC/CuttingStrategy/ContourCuttingStrategy.cs

@@ -11,6 +11,7 @@ namespace OpenNest.CNC.CuttingStrategy
         {
             var exitPoint = approachPoint;
             var entities = partProgram.ToGeometry();
+            entities.RemoveAll(e => e.Layer == SpecialLayers.Rapid);
             var profile = new ShapeProfile(entities);
 
             // Find closest point on perimeter from exit point
@@ -22,7 +23,7 @@ namespace OpenNest.CNC.CuttingStrategy
             orderedCutouts.Reverse();
 
             // Build output program: cutouts first (farthest to nearest), perimeter last
-            var result = new Program();
+            var result = new Program(Mode.Absolute);
             var currentPoint = exitPoint;
 
             foreach (var cutout in orderedCutouts)