fix(gpt6astra): rank lower Priority first and drop etch marks from geometry

Priority was sorted descending, the reverse of the host (StockLadder and
NestJobCandidateComparer treat a lower number as more important), so a
priority-9 part beat a priority-0 part for scarce stock. The existing test
encoded the inverted rule and now asserts the host's direction.

Part geometry filtered only rapids, so scribe/etch moves counted as
material - the bug OpenNest fixed in 1b5e1b1. Use SpecialLayers.IsMaterial.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest.Engine.Gpt6Astra/tests/Gpt6AstraNestingEngineTests.cs

@@ -102,8 +102,11 @@ public class Gpt6AstraNestingEngineTests
     [Fact]
     public void PriorityWinsScarceSpaceAndProgressReflectsCommits()
     {
-        var low = Rectangle("low", 2, 2, 1);
-        var high = new NestJobPart("high", low.Geometry, 1, priority: 9);
+        // Lower Priority number ranks higher, as in StockLadderNestingEngine and
+        // NestJobCandidateComparer; input order is chosen so it cannot decide the winner.
+        var template = Rectangle("template", 2, 2, 1);
+        var low = new NestJobPart("low", template.Geometry, 1, priority: 9);
+        var high = new NestJobPart("high", template.Geometry, 1, priority: 0);
         var job = new NestJob(new[] { low, high }, new[] { new NestPlateStock("s", new Size(2, 2), 1) });
         var updates = new List<NestJobProgress>();
         var result = new Gpt6AstraNestingEngine().Solve(job, new CallbackProgress(updates.Add));
@@ -287,6 +290,31 @@ public class Gpt6AstraNestingEngineTests
         Validate(job, result);
     }
 
+    [Fact]
+    public void EtchMarksAreLeftOutOfNestingGeometry()
+    {
+        // A bend tick starts on material and ends 1.0 into a side notch, outside the part but
+        // inside its bounding box (the PEP case that crashed nesting before 1b5e1b1). As
+        // material it is open geometry leaving the part; as a mark it must be ignored.
+        var job = new NestJob(new[] { new NestJobPart("part", PartGeometrySnapshot.FromProgram(NotchedPartWithEtch()), 2,
+                rotation: RotationPolicy.Fixed(0)) },
+            new[] { new NestPlateStock("s", new Size(10.4, 20.6), 1, partSpacing: 0.2) });
+        var result = new Gpt6AstraNestingEngine().Solve(job);
+        Validate(job, result);
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(2, Assert.Single(result.Plates).Placements.Count);
+    }
+
+    private static Program NotchedPartWithEtch()
+    {
+        var p = new Program();
+        p.MoveTo(0, 0); p.LineTo(10, 0); p.LineTo(10, 4); p.LineTo(8, 4); p.LineTo(8, 6);
+        p.LineTo(10, 6); p.LineTo(10, 10); p.LineTo(0, 10); p.LineTo(0, 0);
+        p.MoveTo(7.5, 5);
+        p.Codes.Add(new LinearMove(9, 5) { Layer = LayerType.Scribe });
+        return p;
+    }
+
     private sealed class CallbackProgress(Action<NestJobProgress> callback) : IProgress<NestJobProgress>
     { public void Report(NestJobProgress value) => callback(value); }
 
@@ -321,7 +349,7 @@ public class Gpt6AstraNestingEngineTests
                 var part = job.Parts.Single(p => p.Id == pose.PartId);
                 Assert.True(part.Rotation.Allows(pose.Rotation));
                 var geometry = ConvertProgram.ToGeometry(DrawingJobMapper.ToProgram(part.Geometry))
-                    .Where(e => !ReferenceEquals(e.Layer, SpecialLayers.Rapid)).ToArray();
+                    .Where(e => SpecialLayers.IsMaterial(e.Layer)).ToArray();
                 foreach (var entity in geometry) { entity.Rotate(pose.Rotation); entity.Offset(pose.X, pose.Y); }
                 var b = (L: geometry.Min(e => e.Left), B: geometry.Min(e => e.Bottom),
                     R: geometry.Max(e => e.Right), T: geometry.Max(e => e.Top));