refactor: move ProgramVariableManager to Core, add config file support

- Move ProgramVariable and ProgramVariableManager from
  OpenNest.Posts.Cincinnati to OpenNest.Core/CNC (namespace OpenNest.CNC)
  so they can be used internally in nest programs
- Add parameterless constructor to CincinnatiPostProcessor that loads
  config from a .json file next to the DLL (creates defaults on first run)
- Enums serialize as readable strings (e.g., "Inches", "ControllerSide")
- Config file: OpenNest.Posts.Cincinnati.json in the Posts/ directory

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

OpenNest.Core/CNC/ProgramVariable.cs

@@ -1,4 +1,4 @@
-namespace OpenNest.Posts.Cincinnati
+namespace OpenNest.CNC
 {
     public sealed class ProgramVariable
     {

OpenNest.Core/CNC/ProgramVariableManager.cs

@@ -2,7 +2,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-namespace OpenNest.Posts.Cincinnati
+namespace OpenNest.CNC
 {
     public sealed class ProgramVariableManager
     {

OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -1,23 +1,63 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Reflection;
 using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using OpenNest.CNC;
 
 namespace OpenNest.Posts.Cincinnati
 {
     public sealed class CincinnatiPostProcessor : IPostProcessor
     {
+        private static readonly JsonSerializerOptions JsonOptions = new()
+        {
+            WriteIndented = true,
+            Converters = { new JsonStringEnumConverter() }
+        };
+
         public string Name => "Cincinnati CL-707";
         public string Author => "OpenNest";
         public string Description => "Cincinnati CL-707/CL-800/CL-900/CL-940/CLX family";
 
         public CincinnatiPostConfig Config { get; }
 
+        public CincinnatiPostProcessor()
+        {
+            var configPath = GetConfigPath();
+            if (File.Exists(configPath))
+            {
+                var json = File.ReadAllText(configPath);
+                Config = JsonSerializer.Deserialize<CincinnatiPostConfig>(json, JsonOptions);
+            }
+            else
+            {
+                Config = new CincinnatiPostConfig();
+                SaveConfig();
+            }
+        }
+
         public CincinnatiPostProcessor(CincinnatiPostConfig config)
         {
             Config = config;
         }
 
+        public void SaveConfig()
+        {
+            var configPath = GetConfigPath();
+            var json = JsonSerializer.Serialize(Config, JsonOptions);
+            File.WriteAllText(configPath, json);
+        }
+
+        private static string GetConfigPath()
+        {
+            var assemblyPath = typeof(CincinnatiPostProcessor).Assembly.Location;
+            var dir = Path.GetDirectoryName(assemblyPath);
+            var name = Path.GetFileNameWithoutExtension(assemblyPath);
+            return Path.Combine(dir, name + ".json");
+        }
+
         public void Post(Nest nest, Stream outputStream)
         {
             // 1. Create variable manager and register standard variables

OpenNest.Posts.Cincinnati/CincinnatiPreambleWriter.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using OpenNest;
+using OpenNest.CNC;
 
 namespace OpenNest.Posts.Cincinnati;
 

OpenNest.Tests/Cincinnati/CincinnatiPostProcessorTests.cs

@@ -1,5 +1,7 @@
 using System.IO;
 using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
 using OpenNest.CNC;
 using OpenNest.Geometry;
 using OpenNest.Posts.Cincinnati;
@@ -96,6 +98,47 @@ public class CincinnatiPostProcessorTests
         }
     }
 
+    [Fact]
+    public void Config_RoundTripsAsJson()
+    {
+        var config = new CincinnatiPostConfig
+        {
+            ConfigurationName = "CL940_CORONA",
+            DefaultLibraryFile = "MS135N2PANEL.lib",
+            PostedUnits = Units.Inches,
+            KerfCompensation = KerfMode.ControllerSide,
+            UseAntiDive = true
+        };
+
+        var opts = new JsonSerializerOptions
+        {
+            WriteIndented = true,
+            Converters = { new JsonStringEnumConverter() }
+        };
+        var json = JsonSerializer.Serialize(config, opts);
+        var deserialized = JsonSerializer.Deserialize<CincinnatiPostConfig>(json, opts);
+
+        Assert.Equal("CL940_CORONA", deserialized.ConfigurationName);
+        Assert.Equal("MS135N2PANEL.lib", deserialized.DefaultLibraryFile);
+        Assert.Equal(Units.Inches, deserialized.PostedUnits);
+        Assert.Equal(KerfMode.ControllerSide, deserialized.KerfCompensation);
+        Assert.True(deserialized.UseAntiDive);
+
+        // Enums serialize as strings
+        Assert.Contains("\"Inches\"", json);
+        Assert.Contains("\"ControllerSide\"", json);
+    }
+
+    [Fact]
+    public void ParameterlessConstructor_LoadsOrCreatesConfig()
+    {
+        // The parameterless constructor reads from a .json file next to the assembly,
+        // or creates defaults if none exists. Either way, Config should be non-null.
+        var post = new CincinnatiPostProcessor();
+        Assert.NotNull(post.Config);
+        Assert.Equal("CL940", post.Config.ConfigurationName);
+    }
+
     private static Nest CreateTestNest()
     {
         var nest = new Nest("TestNest");

OpenNest.Tests/Cincinnati/CincinnatiPreambleWriterTests.cs

@@ -1,5 +1,6 @@
 using System.IO;
 using System.Text;
+using OpenNest.CNC;
 using OpenNest.Posts.Cincinnati;
 
 namespace OpenNest.Tests.Cincinnati;

OpenNest.Tests/Cincinnati/ProgramVariableManagerTests.cs

@@ -1,4 +1,4 @@
-using OpenNest.Posts.Cincinnati;
+using OpenNest.CNC;
 
 namespace OpenNest.Tests.Cincinnati;