feat(posts): let posts load and save their settings as JSON

IJsonConfigPostProcessor lets a host keep a post's settings somewhere other
than the JSON file beside the post DLL. The CL-707, CI Fiber and Gravograph
posts implement it; LoadConfig keeps the current settings when the JSON is
unusable.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest.Core/IJsonConfigPostProcessor.cs

@@ -0,0 +1,19 @@
+namespace OpenNest
+{
+    /// <summary>
+    /// A configurable post whose settings travel as JSON, so a host can keep them somewhere other
+    /// than the post's own file (the nest server's shared copy, for one).
+    /// </summary>
+    public interface IJsonConfigPostProcessor : IConfigurablePostProcessor
+    {
+        /// <summary>The settings as the post's own file holds them.</summary>
+        string SerializeConfig();
+
+        /// <summary>
+        /// Replaces the settings with <paramref name="json"/>, in the post's file format; the
+        /// file itself is not written. Throws <see cref="System.Text.Json.JsonException"/> and
+        /// keeps the current settings when the JSON is not usable.
+        /// </summary>
+        void LoadConfig(string json);
+    }
+}

Posts/OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -10,7 +10,7 @@ using OpenNest.CNC;
 namespace OpenNest.Posts.Cincinnati
 {
     public sealed class CincinnatiPostProcessor
-        : IConfigurablePostProcessor,
+        : IJsonConfigPostProcessor,
             IPostProcessorNestAware,
             IMaterialProvidingPostProcessor
     {
@@ -24,7 +24,7 @@ namespace OpenNest.Posts.Cincinnati
         public string Author => "OpenNest";
         public string Description => "Cincinnati CL-707/CL-800/CL-900/CL-940/CLX family";
 
-        public CincinnatiPostConfig Config { get; }
+        public CincinnatiPostConfig Config { get; private set; }
 
         object IConfigurablePostProcessor.Config => Config;
 
@@ -81,10 +81,17 @@ namespace OpenNest.Posts.Cincinnati
         public void SaveConfig()
         {
             var configPath = GetConfigPath();
-            var json = JsonSerializer.Serialize(Config, JsonOptions);
+            var json = SerializeConfig();
             File.WriteAllText(configPath, json);
         }
 
+        public string SerializeConfig() => JsonSerializer.Serialize(Config, JsonOptions);
+
+        public void LoadConfig(string json) =>
+            Config =
+                JsonSerializer.Deserialize<CincinnatiPostConfig>(json, JsonOptions)
+                ?? throw new JsonException("The post settings are empty.");
+
         private static string GetConfigPath()
         {
             var assemblyPath = typeof(CincinnatiPostProcessor).Assembly.Location;

Posts/OpenNest.Posts.CincinnatiCIFiber/CIFiberPostProcessor.cs

@@ -17,7 +17,7 @@ namespace OpenNest.Posts.CincinnatiCIFiber
     /// structure of the machine sample (see <see cref="CIFiberProgramWriter"/>).
     /// </summary>
     public sealed class CIFiberPostProcessor
-        : IConfigurablePostProcessor,
+        : IJsonConfigPostProcessor,
             IMultiFilePostProcessor,
             IPostVerificationSupport
     {
@@ -33,7 +33,7 @@ namespace OpenNest.Posts.CincinnatiCIFiber
         public string Description =>
             "CI Fiber family laser (TF5200 / nLight CLX), e.g. CI Fiber 4020 8kW";
 
-        public CIFiberPostConfig Config { get; }
+        public CIFiberPostConfig Config { get; private set; }
 
         object IConfigurablePostProcessor.Config => Config;
 
@@ -62,10 +62,17 @@ namespace OpenNest.Posts.CincinnatiCIFiber
         public void SaveConfig()
         {
             var configPath = GetConfigPath();
-            var json = JsonSerializer.Serialize(Config, JsonOptions);
+            var json = SerializeConfig();
             File.WriteAllText(configPath, json);
         }
 
+        public string SerializeConfig() => JsonSerializer.Serialize(Config, JsonOptions);
+
+        public void LoadConfig(string json) =>
+            Config =
+                JsonSerializer.Deserialize<CIFiberPostConfig>(json, JsonOptions)
+                ?? throw new JsonException("The post settings are empty.");
+
         private static string GetConfigPath()
         {
             var assemblyPath = typeof(CIFiberPostProcessor).Assembly.Location;

Posts/OpenNest.Posts.GravographIS/GravographISPostProcessor.cs

@@ -17,7 +17,7 @@ namespace OpenNest.Posts.GravographIS
     /// (Scribe) and a cut pass (Cut), each with its own feed/depth from <see cref="Config"/>.
     /// The cut pass pauses by default so the operator can swap/adjust the tool.
     /// </summary>
-    public sealed class GravographISPostProcessor : IConfigurablePostProcessor
+    public sealed class GravographISPostProcessor : IJsonConfigPostProcessor
     {
         private static readonly JsonSerializerOptions JsonOptions = new()
         {
@@ -38,7 +38,7 @@ namespace OpenNest.Posts.GravographIS
 
         public bool AllowReverse { get; set; } = true;
 
-        public GravographISPostConfig Config { get; }
+        public GravographISPostConfig Config { get; private set; }
 
         object IConfigurablePostProcessor.Config => Config;
 
@@ -67,10 +67,17 @@ namespace OpenNest.Posts.GravographIS
         public void SaveConfig()
         {
             var configPath = GetConfigPath();
-            var json = JsonSerializer.Serialize(Config, JsonOptions);
+            var json = SerializeConfig();
             File.WriteAllText(configPath, json);
         }
 
+        public string SerializeConfig() => JsonSerializer.Serialize(Config, JsonOptions);
+
+        public void LoadConfig(string json) =>
+            Config =
+                JsonSerializer.Deserialize<GravographISPostConfig>(json, JsonOptions)
+                ?? throw new JsonException("The post settings are empty.");
+
         private static string GetConfigPath()
         {
             var assemblyPath = typeof(GravographISPostProcessor).Assembly.Location;