fix(opus55): cut clearance margin to 0.003 and drop etch marks from geometry

The 0.022 margin assumed validators flatten arcs at 0.01; NestValidator
uses 0.001, so a pair can read at most 0.002 closer than true. 0.003
covers that plus the 1e-4 Clipper grid, returning ~0.019 per gap. Arc,
disc, obround and zero-spacing tests still pass.

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.Opus55/Opus55NestingEngine.cs

@@ -20,11 +20,15 @@ namespace OpenNest.Engine.Opus55;
 public sealed class Opus55NestingEngine : INestingEngine
 {
     /// <summary>
-    /// Extra clearance beyond the stock's part spacing, in job units. Validators polygonize arcs
+    /// Extra clearance beyond the stock's part spacing, in job units. Footprints already contain
-    /// circumscribed at 0.01 per side, so two tangent true arcs can read as up to 0.02 closer
+    /// the true outline grown by half the clearance (chord tolerance is added separately), so this
-    /// than they are; the rest absorbs Clipper's 1e-4 grid and inner-fit clamping.
+    /// only has to cover the validator's side: NestValidator flattens each perimeter within
+    /// 0.001 of the true arc (OutlineTolerance), so two true arcs can read up to 0.002 closer
+    /// than they are. The remaining 0.001 absorbs the 1e-4 Clipper grid on both sides (footprint
+    /// offset, Minkowski union, free-region difference, the validator's own offset); the
+    /// validator's round-join chord error (0.0001) only ever makes it more lenient.
     /// </summary>
-    internal const double ClearanceMargin = 0.022;
+    internal const double ClearanceMargin = 0.003;
 
     /// <summary>Strategy variants, tried in order: (front direction, area exponent beta).</summary>
     private static readonly (PackAxis Axis, double Beta)[] Variants =

OpenNest.Engine.Opus55/PartCatalog.cs

@@ -111,7 +111,7 @@ internal static class PartCatalog
     {
         var entities = ConvertProgram
             .ToGeometry(DrawingJobMapper.ToProgram(geometry))
-            .Where(e => !ReferenceEquals(e.Layer, SpecialLayers.Rapid))
+            .Where(e => SpecialLayers.IsMaterial(e.Layer))
             .ToList();
         if (entities.Count == 0)
             return null;

OpenNest.Engine.Opus55/README.md

@@ -15,9 +15,9 @@ Every placement decision (which part, which rotation, where, on which sheet) com
   angles plus the two orientations that axis-align the minimum-area bounding rectangle
   (`RotatingCalipers`); for sweeps, up to 8 evenly spaced legal steps. Point-symmetric duplicates are dropped.
 - Each orientation gets a **footprint**: outline inflated (miter joins, so it contains the exact
-  round offset) by `(spacing + 0.022) / 2 + chordTolerance`. Two parts respect the spacing
+  round offset) by `(spacing + 0.003) / 2 + chordTolerance`. Two parts respect the spacing
-  when their footprints don't overlap. The 0.022 covers validators that polygonize arcs
+  when their footprints don't overlap. The 0.003 covers `NestValidator` flattening each arc
-  circumscribed at 0.01 per side, plus Clipper's 1e-4 grid.
+  within 0.001 of true (0.002 for a pair), plus Clipper's 1e-4 grid on both sides.
 - **No-fit polygons** between footprints come from Clipper2 Minkowski sums: an O(n+m)
   edge merge for convex pairs, and for concave pairs the boundary sweep ∪ (A + p₀) ∪ (−B + a₀).
   The last two terms cover "B inside A" and "B swallows A". NFPs are cached per orientation pair.
@@ -83,9 +83,10 @@ The engine reports as `Opus55NestingEngine`.
 ## Known limitations
 
 - **No part-in-part:** holes are treated as solid, so small parts never nest inside cutouts.
-- **Clearance padding:** gaps are ~0.022 (plus up to the chord tolerance) wider than the
+- **Clearance padding:** gaps are ~0.003 (plus up to the chord tolerance) wider than the
-  required spacing, to stay valid under circumscribed-polygon validators. That's negligible in mm
+  required spacing, to stay valid under `NestValidator`'s 0.001 arc flattening. The margin was
-  and about 0.02" in inches. The constants are absolute and assume job units near inch/mm scale.
+  0.022 while it assumed a 0.01 validator tolerance. The constants are absolute and assume job
+  units near inch/mm scale.
 - **Rotation coverage:** `Automatic` parts try at most 8 orientations (fewer when a job has many
   distinct parts: `48 / partCount`, minimum 2). Free-angle rotations aren't explored beyond the MBR alignment.
 - **Greedy core:** there is no order/permutation search. The variants and tail re-plan are the only

OpenNest.Engine.Opus55/tests/Opus55NestingEngineTests.cs

@@ -191,6 +191,24 @@ public class Opus55NestingEngineTests
         Assert.Equal(Describe(first), Describe(second));
     }
 
+    [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 etched = Polyline((0, 0), (10, 0), (10, 4), (8, 4), (8, 6), (10, 6), (10, 10), (0, 10));
+        etched.Codes.Add(new RapidMove(7.5, 5));
+        etched.Codes.Add(new LinearMove(9, 5) { Layer = LayerType.Scribe });
+        var job = Job(new[] { Part("part", etched, 2, RotationPolicy.Fixed(0)) }, new[] { Stock("sheet", 10.4, 20.6, spacing: 0.2) });
+
+        var result = new Opus55NestingEngine().Solve(job);
+
+        AssertValid(job, result);
+        Assert.Equal(NestJobStatus.Complete, result.Status);
+        Assert.Equal(2, Assert.Single(result.Plates).Placements.Count);
+    }
+
     [Fact]
     public void HasPublicParameterlessConstructorForPluginDiscovery()
     {