feat: add CincinnatiPostProcessor implementing IPostProcessor

Orchestrates CincinnatiPreambleWriter and CincinnatiSheetWriter to produce
a complete Cincinnati CNC output file from a Nest; includes 4 integration tests.

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

OpenNest.Tests/Cincinnati/CincinnatiPostProcessorTests.cs

@@ -0,0 +1,122 @@
+using System.IO;
+using System.Text;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.Posts.Cincinnati;
+
+namespace OpenNest.Tests.Cincinnati;
+
+public class CincinnatiPostProcessorTests
+{
+    [Fact]
+    public void Post_ProducesOutput_ForSinglePlateNest()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig
+        {
+            ConfigurationName = "CL940",
+            DefaultLibraryFile = "MS135N2PANEL.lib",
+            PostedAccuracy = 4
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+
+        // Main program elements
+        Assert.Contains("( NEST TestNest )", output);
+        Assert.Contains("( CONFIGURATION - CL940 )", output);
+        Assert.Contains("G20", output);
+        Assert.Contains("M30 (END OF MAIN)", output);
+
+        // Variable declaration
+        Assert.Contains(":100", output);
+        Assert.Contains("#126=", output);
+
+        // Sheet subprogram
+        Assert.Contains(":101", output);
+        Assert.Contains("( Sheet 1 )", output);
+        Assert.Contains("G84", output);
+        Assert.Contains("M99", output);
+    }
+
+    [Fact]
+    public void Post_ImplementsIPostProcessor()
+    {
+        var post = new CincinnatiPostProcessor(new CincinnatiPostConfig());
+        IPostProcessor pp = post;
+
+        Assert.Equal("Cincinnati CL-707", pp.Name);
+        Assert.Equal("OpenNest", pp.Author);
+    }
+
+    [Fact]
+    public void Post_SkipsEmptyPlates()
+    {
+        var nest = new Nest("TestNest");
+        nest.Plates.Add(new Plate(48, 96)); // empty plate
+        var plate2 = new Plate(48, 96);
+        plate2.Parts.Add(new Part(new Drawing("Part1", CreateSquareProgram())));
+        nest.Plates.Add(plate2);
+
+        var config = new CincinnatiPostConfig { PostedAccuracy = 4 };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+
+        // Should only have one sheet subprogram call in main
+        Assert.Contains("N1M98 P101 (SHEET 1)", output);
+        Assert.DoesNotContain("SHEET 2", output);
+    }
+
+    [Fact]
+    public void Post_ToFile_CreatesFile()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig { PostedAccuracy = 4 };
+        var post = new CincinnatiPostProcessor(config);
+        var tempFile = Path.GetTempFileName() + ".CNC";
+
+        try
+        {
+            post.Post(nest, tempFile);
+            Assert.True(File.Exists(tempFile));
+            var content = File.ReadAllText(tempFile);
+            Assert.Contains("M30", content);
+        }
+        finally
+        {
+            if (File.Exists(tempFile))
+                File.Delete(tempFile);
+        }
+    }
+
+    private static Nest CreateTestNest()
+    {
+        var nest = new Nest("TestNest");
+        var drawing = new Drawing("Square", CreateSquareProgram());
+        nest.Drawings.Add(drawing);
+
+        var plate = new Plate(48.0, 96.0);
+        plate.Parts.Add(new Part(drawing, new Vector(10, 10)));
+        nest.Plates.Add(plate);
+
+        return nest;
+    }
+
+    private static Program CreateSquareProgram()
+    {
+        var pgm = new Program();
+        pgm.Codes.Add(new RapidMove(0, 0));
+        pgm.Codes.Add(new LinearMove(2, 0));
+        pgm.Codes.Add(new LinearMove(2, 2));
+        pgm.Codes.Add(new LinearMove(0, 2));
+        pgm.Codes.Add(new LinearMove(0, 0));
+        return pgm;
+    }
+}