feat: add ProgramVariable and ProgramVariableManager for macro variable declarations

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

OpenNest.Tests/Cincinnati/ProgramVariableManagerTests.cs

@@ -0,0 +1,71 @@
+using OpenNest.Posts.Cincinnati;
+
+namespace OpenNest.Tests.Cincinnati;
+
+public class ProgramVariableManagerTests
+{
+    [Fact]
+    public void GetOrCreate_ReturnsNewVariable()
+    {
+        var mgr = new ProgramVariableManager();
+        var v = mgr.GetOrCreate("LeadInFeedrate", 126);
+        Assert.Equal(126, v.Number);
+        Assert.Equal("LeadInFeedrate", v.Name);
+    }
+
+    [Fact]
+    public void GetOrCreate_ReturnsSameVariable_WhenCalledTwice()
+    {
+        var mgr = new ProgramVariableManager();
+        var v1 = mgr.GetOrCreate("LeadInFeedrate", 126);
+        var v2 = mgr.GetOrCreate("LeadInFeedrate", 126);
+        Assert.Same(v1, v2);
+    }
+
+    [Fact]
+    public void GetOrCreate_WithExpression_SetsExpression()
+    {
+        var mgr = new ProgramVariableManager();
+        var v = mgr.GetOrCreate("LeadInFeedrate", 126, "[#148*0.5]");
+        Assert.Equal("[#148*0.5]", v.Expression);
+    }
+
+    [Fact]
+    public void GetOrCreate_WithLiteral_SetsExpression()
+    {
+        var mgr = new ProgramVariableManager();
+        var v = mgr.GetOrCreate("CircleFeedrate", 128, ".8");
+        Assert.Equal(".8", v.Expression);
+    }
+
+    [Fact]
+    public void Reference_ReturnsHashNumber()
+    {
+        var v = new ProgramVariable(126, "LeadInFeedrate");
+        Assert.Equal("#126", v.Reference);
+    }
+
+    [Fact]
+    public void EmitDeclarations_ProducesCorrectLines()
+    {
+        var mgr = new ProgramVariableManager();
+        mgr.GetOrCreate("LeadInFeedrate", 126, "[#148*0.5]");
+        mgr.GetOrCreate("CircleFeedrate", 128, ".8");
+
+        var lines = mgr.EmitDeclarations();
+
+        Assert.Contains("#126=[#148*0.5] (LEAD IN FEEDRATE)", lines);
+        Assert.Contains("#128=.8 (CIRCLE FEEDRATE)", lines);
+    }
+
+    [Fact]
+    public void EmitDeclarations_SkipsVariablesWithNoExpression()
+    {
+        var mgr = new ProgramVariableManager();
+        mgr.GetOrCreate("ProcessFeedrate", 148);
+
+        var lines = mgr.EmitDeclarations();
+
+        Assert.Empty(lines);
+    }
+}