feat: adaptive arc segmentation based on chord tolerance

Add SegmentsForTolerance(double) to Arc and Circle that calculates the
minimum segments needed to keep sagitta within the given tolerance.
Add Shape.ToPolygonWithTolerance() that uses it per arc/circle.

Push distance now uses 0.08" chord tolerance instead of a fixed segment
count, giving appropriate resolution for each arc based on its radius.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.Core/Geometry/Shape.cs

@@ -243,6 +243,49 @@ namespace OpenNest.Geometry
             return polygon;
         }
 
+        /// <summary>
+        /// Converts the shape to a polygon using a chord tolerance to determine
+        /// the number of segments per arc/circle.
+        /// </summary>
+        public Polygon ToPolygonWithTolerance(double tolerance)
+        {
+            var polygon = new Polygon();
+
+            foreach (var entity in Entities)
+            {
+                switch (entity.Type)
+                {
+                    case EntityType.Arc:
+                        var arc = (Arc)entity;
+                        polygon.Vertices.AddRange(arc.ToPoints(arc.SegmentsForTolerance(tolerance)));
+                        break;
+
+                    case EntityType.Line:
+                        var line = (Line)entity;
+                        polygon.Vertices.AddRange(new[]
+                        {
+                            line.StartPoint,
+                            line.EndPoint
+                        });
+                        break;
+
+                    case EntityType.Circle:
+                        var circle = (Circle)entity;
+                        polygon.Vertices.AddRange(circle.ToPoints(circle.SegmentsForTolerance(tolerance)));
+                        break;
+
+                    default:
+                        Debug.Fail("Unhandled geometry type");
+                        break;
+                }
+            }
+
+            polygon.Close();
+            polygon.Cleanup();
+
+            return polygon;
+        }
+
         /// <summary>
         /// Reverses the rotation direction of the shape.
         /// </summary>