feat: serialize and deserialize hole sub-programs in nest file format

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

OpenNest.Tests/IO/SubProgramSerializationTests.cs

@@ -0,0 +1,75 @@
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.IO;
+
+namespace OpenNest.Tests.IO;
+
+public class SubProgramSerializationTests
+{
+    [Fact]
+    public void NestWriter_WritesSubProgramCall_WithOffset()
+    {
+        var nest = CreateNestWithHoleSubProgram();
+
+        using var stream = new MemoryStream();
+        var writer = new NestWriter(nest);
+        writer.Write(stream);
+        stream.Position = 0;
+
+        var reader = new NestReader(stream);
+        var loaded = reader.Read();
+
+        var drawing = loaded.Drawings.First();
+        var calls = drawing.Program.Codes.OfType<SubProgramCall>().ToList();
+        Assert.Single(calls);
+        Assert.Equal(5, calls[0].Offset.X, 1);
+        Assert.Equal(5, calls[0].Offset.Y, 1);
+    }
+
+    [Fact]
+    public void NestWriter_WritesSubPrograms_AndRestoresOnLoad()
+    {
+        var nest = CreateNestWithHoleSubProgram();
+
+        using var stream = new MemoryStream();
+        var writer = new NestWriter(nest);
+        writer.Write(stream);
+        stream.Position = 0;
+
+        var reader = new NestReader(stream);
+        var loaded = reader.Read();
+
+        var drawing = loaded.Drawings.First();
+        Assert.True(drawing.Program.SubPrograms.Count > 0);
+
+        var call = drawing.Program.Codes.OfType<SubProgramCall>().First();
+        Assert.True(drawing.Program.SubPrograms.ContainsKey(call.Id));
+    }
+
+    private static Nest CreateNestWithHoleSubProgram()
+    {
+        var sub = new Program(Mode.Incremental);
+        sub.Codes.Add(new LinearMove(0.1, 0) { Layer = LayerType.Leadin });
+        sub.Codes.Add(new ArcMove(new Vector(0, 0), new Vector(-0.5, 0), RotationType.CW));
+
+        var pgm = new Program(Mode.Absolute);
+        pgm.SubPrograms[42] = sub;
+        pgm.Codes.Add(new SubProgramCall { Id = 42, Program = sub, Offset = new Vector(5, 5) });
+        // Add perimeter so the drawing has non-zero geometry
+        pgm.Codes.Add(new RapidMove(0, 0));
+        pgm.Codes.Add(new LinearMove(10, 0));
+        pgm.Codes.Add(new LinearMove(10, 10));
+        pgm.Codes.Add(new LinearMove(0, 10));
+        pgm.Codes.Add(new LinearMove(0, 0));
+
+        var drawing = new Drawing("TestPart") { Program = pgm };
+        var nest = new Nest();
+        nest.Drawings.Add(drawing);
+
+        var plate = new Plate { Size = new Size(48, 96) };
+        plate.Parts.Add(new Part(drawing));
+        nest.Plates.Add(plate);
+
+        return nest;
+    }
+}