feat: serialize/deserialize bends in nest file format

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

OpenNest.Tests/NestBendSerializationTests.cs

@@ -0,0 +1,91 @@
+using OpenNest.Bending;
+using OpenNest.Geometry;
+using OpenNest.IO;
+using System.Linq;
+
+namespace OpenNest.Tests;
+
+public class NestBendSerializationTests
+{
+    [Fact]
+    public void Bends_SurviveNestRoundtrip()
+    {
+        var drawing = TestHelpers.MakeSquareDrawing();
+        drawing.Bends.Add(new Bend
+        {
+            StartPoint = new Vector(0, 5),
+            EndPoint = new Vector(10, 5),
+            Direction = BendDirection.Up,
+            Angle = 90,
+            Radius = 0.06,
+            NoteText = "UP 90° R0.06"
+        });
+        drawing.Bends.Add(new Bend
+        {
+            StartPoint = new Vector(0, 3),
+            EndPoint = new Vector(10, 3),
+            Direction = BendDirection.Down,
+            Angle = 45.5,
+            Radius = 0.125,
+            NoteText = "DOWN 45.5° R0.125"
+        });
+
+        var nest = new Nest();
+        nest.Drawings.Add(drawing);
+        var plate = new Plate(60, 120);
+        plate.GrainAngle = 0.5236;
+        plate.Parts.Add(new Part(drawing, new Vector(0, 0)));
+        nest.Plates.Add(plate);
+
+        using var ms = new MemoryStream();
+        var writer = new NestWriter(nest);
+        writer.Write(ms);
+
+        ms.Position = 0;
+        var reader = new NestReader(ms);
+        var loaded = reader.Read();
+
+        var loadedDrawing = loaded.Drawings.First();
+        Assert.Equal(2, loadedDrawing.Bends.Count);
+
+        var bend1 = loadedDrawing.Bends[0];
+        Assert.Equal(0, bend1.StartPoint.X, 0.001);
+        Assert.Equal(5, bend1.StartPoint.Y, 0.001);
+        Assert.Equal(10, bend1.EndPoint.X, 0.001);
+        Assert.Equal(5, bend1.EndPoint.Y, 0.001);
+        Assert.Equal(BendDirection.Up, bend1.Direction);
+        Assert.Equal(90, bend1.Angle);
+        Assert.Equal(0.06, bend1.Radius);
+        Assert.Equal("UP 90° R0.06", bend1.NoteText);
+
+        var bend2 = loadedDrawing.Bends[1];
+        Assert.Equal(BendDirection.Down, bend2.Direction);
+        Assert.Equal(45.5, bend2.Angle);
+
+        var loadedPlate = loaded.Plates[0];
+        Assert.Equal(0.5236, loadedPlate.GrainAngle, 0.0001);
+    }
+
+    [Fact]
+    public void NoBends_SurviveNestRoundtrip()
+    {
+        var drawing = TestHelpers.MakeSquareDrawing();
+
+        var nest = new Nest();
+        nest.Drawings.Add(drawing);
+        var plate = new Plate(60, 120);
+        plate.Parts.Add(new Part(drawing, new Vector(0, 0)));
+        nest.Plates.Add(plate);
+
+        using var ms = new MemoryStream();
+        var writer = new NestWriter(nest);
+        writer.Write(ms);
+
+        ms.Position = 0;
+        var reader = new NestReader(ms);
+        var loaded = reader.Read();
+
+        Assert.Empty(loaded.Drawings.First().Bends);
+        Assert.Equal(0, loaded.Plates[0].GrainAngle);
+    }
+}