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.Tests/MotionSuppressedTests.cs

@@ -0,0 +1,45 @@
+using OpenNest.CNC;
+using OpenNest.Geometry;
+
+namespace OpenNest.Tests;
+
+public class MotionSuppressedTests
+{
+    [Fact]
+    public void LinearMove_Suppressed_DefaultsFalse()
+    {
+        var move = new LinearMove(new Vector(1, 2));
+        Assert.False(move.Suppressed);
+    }
+
+    [Fact]
+    public void ArcMove_Suppressed_DefaultsFalse()
+    {
+        var move = new ArcMove(new Vector(1, 2), new Vector(0, 0));
+        Assert.False(move.Suppressed);
+    }
+
+    [Fact]
+    public void RapidMove_Suppressed_DefaultsFalse()
+    {
+        var move = new RapidMove(new Vector(1, 2));
+        Assert.False(move.Suppressed);
+    }
+
+    [Fact]
+    public void Suppressed_CanBeSet()
+    {
+        var move = new LinearMove(new Vector(1, 2));
+        move.Suppressed = true;
+        Assert.True(move.Suppressed);
+    }
+
+    [Fact]
+    public void Clone_PreservesSuppressed()
+    {
+        var move = new LinearMove(new Vector(1, 2));
+        move.Suppressed = true;
+        var clone = (LinearMove)move.Clone();
+        Assert.True(clone.Suppressed);
+    }
+}