feat: add Motion.Suppressed property to mark tab-gap codes

Adds Suppressed bool to the Motion base class so LinearMove, ArcMove,
and RapidMove can be flagged for skip during rendering and post-processing
when they fall within a tab gap. Clone() updated on all three subclasses
to preserve the flag. Covered by new MotionSuppressedTests.

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

OpenNest.Core/CNC/RapidMove.cs

@@ -26,7 +26,10 @@ namespace OpenNest.CNC
 
         public override ICode Clone()
         {
-            return new RapidMove(EndPoint);
+            return new RapidMove(EndPoint)
+            {
+                Suppressed = Suppressed
+            };
         }
 
         public override string ToString()