feat: add CincinnatiPreambleWriter for main program and variable declaration

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

OpenNest.Posts.Cincinnati/CincinnatiPreambleWriter.cs

@@ -0,0 +1,72 @@
+using System;
+using System.IO;
+using OpenNest;
+
+namespace OpenNest.Posts.Cincinnati;
+
+/// <summary>
+/// Emits the main program header and variable declaration subprogram
+/// for a Cincinnati laser post-processor output file.
+/// </summary>
+public sealed class CincinnatiPreambleWriter
+{
+    private readonly CincinnatiPostConfig _config;
+
+    public CincinnatiPreambleWriter(CincinnatiPostConfig config)
+    {
+        _config = config;
+    }
+
+    /// <summary>
+    /// Writes the main program header block.
+    /// </summary>
+    public void WriteMainProgram(TextWriter w, string nestName, string materialDescription, int sheetCount)
+    {
+        w.WriteLine(CoordinateFormatter.Comment($"NEST {nestName}"));
+        w.WriteLine(CoordinateFormatter.Comment($"CONFIGURATION - {_config.ConfigurationName}"));
+        w.WriteLine(CoordinateFormatter.Comment(DateTime.Now.ToString("MM-dd-yyyy hh:mm:ss tt")));
+
+        if (!string.IsNullOrEmpty(materialDescription))
+            w.WriteLine(CoordinateFormatter.Comment($"Material = {materialDescription}"));
+
+        if (_config.UseExactStopMode)
+            w.WriteLine("G61");
+
+        w.WriteLine(CoordinateFormatter.Comment("MAIN PROGRAM"));
+
+        w.WriteLine(_config.PostedUnits == Units.Millimeters ? "G21" : "G20");
+
+        w.WriteLine("M42");
+
+        if (_config.ProcessParameterMode == G89Mode.LibraryFile && !string.IsNullOrEmpty(_config.DefaultLibraryFile))
+            w.WriteLine($"G89 P {_config.DefaultLibraryFile}");
+
+        w.WriteLine($"M98 P{_config.VariableDeclarationSubprogram} (Variable Declaration)");
+
+        w.WriteLine("GOTO1 (GOTO SHEET NUMBER)");
+
+        for (var i = 1; i <= sheetCount; i++)
+        {
+            var subNum = _config.SheetSubprogramStart + (i - 1);
+            w.WriteLine($"N{i}M98 P{subNum} (SHEET {i})");
+        }
+
+        w.WriteLine("M42");
+        w.WriteLine("M30 (END OF MAIN)");
+    }
+
+    /// <summary>
+    /// Writes the variable declaration subprogram block.
+    /// </summary>
+    public void WriteVariableDeclaration(TextWriter w, ProgramVariableManager vars)
+    {
+        w.WriteLine("(*****************************************************)");
+        w.WriteLine($":{_config.VariableDeclarationSubprogram}");
+        w.WriteLine("(Variable Declaration Start)");
+
+        foreach (var line in vars.EmitDeclarations())
+            w.WriteLine(line);
+
+        w.WriteLine("M99 (Variable Declaration End)");
+    }
+}