feat: add Variables dictionary to Program with deep-copy in Clone

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

OpenNest.Core/CNC/Program.cs

@@ -1,6 +1,7 @@
 using OpenNest.Converters;
 using OpenNest.Geometry;
 using OpenNest.Math;
+using System;
 using System.Collections.Generic;
 
 namespace OpenNest.CNC
@@ -9,6 +10,8 @@ namespace OpenNest.CNC
     {
         public List<ICode> Codes;
 
+        public Dictionary<string, VariableDefinition> Variables { get; } = new(StringComparer.OrdinalIgnoreCase);
+
         private Mode mode;
 
         public Program(Mode mode = Mode.Absolute)
@@ -454,6 +457,9 @@ namespace OpenNest.CNC
 
             pgm.Codes.AddRange(codes);
 
+            foreach (var kvp in Variables)
+                pgm.Variables[kvp.Key] = kvp.Value;
+
             return pgm;
         }
 

OpenNest.Tests/CNC/ProgramVariableTests.cs

@@ -101,4 +101,35 @@ public class ProgramVariableTests
         move.Offset(5.0, 0);
         Assert.Null(move.VariableRefs);
     }
+
+    [Fact]
+    public void Program_Variables_EmptyByDefault()
+    {
+        var pgm = new Program();
+        Assert.Empty(pgm.Variables);
+    }
+
+    [Fact]
+    public void Program_Variables_CaseInsensitive()
+    {
+        var pgm = new Program();
+        pgm.Variables["Diameter"] = new VariableDefinition("Diameter", "0.3", 0.3);
+        Assert.True(pgm.Variables.ContainsKey("diameter"));
+    }
+
+    [Fact]
+    public void Program_Clone_DeepCopiesVariables()
+    {
+        var pgm = new Program();
+        pgm.Variables["diameter"] = new VariableDefinition("diameter", "0.3", 0.3);
+        pgm.Codes.Add(new LinearMove(1.0, 0));
+
+        var clone = (Program)pgm.Clone();
+
+        Assert.Single(clone.Variables);
+        Assert.Equal(0.3, clone.Variables["diameter"].Value);
+        // Verify it's a separate dictionary
+        clone.Variables.Remove("diameter");
+        Assert.Single(pgm.Variables);
+    }
 }