fix: address review findings — input validation, exception handling, cleanup

Add argument validation to EllipseConverter.Convert for tolerance and
semi-axis parameters. Narrow bare catch in Extensions.cs spline method
to log via Debug.WriteLine. Remove unused lineCount variable from
SolidWorksBendDetectorTests.

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

OpenNest.Core/Geometry/EllipseConverter.cs

@@ -67,6 +67,11 @@ namespace OpenNest.Geometry
         public static List<Entity> Convert(Vector center, double semiMajor, double semiMinor,
             double rotation, double startParam, double endParam, double tolerance = 0.001)
         {
+            if (tolerance <= 0)
+                throw new ArgumentOutOfRangeException(nameof(tolerance), "Tolerance must be positive.");
+            if (semiMajor <= 0 || semiMinor <= 0)
+                throw new ArgumentOutOfRangeException("Semi-axis lengths must be positive.");
+
             if (endParam <= startParam)
                 endParam += Angle.TwoPI;
 

OpenNest.IO/Extensions.cs

@@ -1,6 +1,7 @@
 using ACadSharp.Entities;
 using CSMath;
 using OpenNest.Geometry;
+using System;
 using System.Collections.Generic;
 using System.Drawing;
 using System.Linq;
@@ -68,8 +69,9 @@ namespace OpenNest.IO
             {
                 curvePoints = spline.PolygonalVertexes(precision > 0 ? precision : 200);
             }
-            catch
+            catch (Exception ex)
             {
+                System.Diagnostics.Debug.WriteLine($"Spline curve evaluation failed: {ex.Message}");
                 curvePoints = null;
             }
 

OpenNest.Tests/Bending/SolidWorksBendDetectorTests.cs

@@ -70,7 +70,6 @@ public class SolidWorksBendDetectorTests
         // changing the entity count. Verify arcs are present and no
         // spurious closing chord exists.
         var arcCount = result.Entities.Count(e => e is OpenNest.Geometry.Arc);
-        var lineCount = result.Entities.Count(e => e is OpenNest.Geometry.Line);
         var circleCount = result.Entities.Count(e => e is OpenNest.Geometry.Circle);
 
         Assert.True(arcCount > 0, "Expected arcs from ellipse conversion");