feat: add IConfigurablePostProcessor interface and implement in Cincinnati post

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

OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -9,7 +9,7 @@ using OpenNest.CNC;
 
 namespace OpenNest.Posts.Cincinnati
 {
-    public sealed class CincinnatiPostProcessor : IPostProcessor
+    public sealed class CincinnatiPostProcessor : IConfigurablePostProcessor
     {
         private static readonly JsonSerializerOptions JsonOptions = new()
         {
@@ -23,6 +23,8 @@ namespace OpenNest.Posts.Cincinnati
 
         public CincinnatiPostConfig Config { get; }
 
+        object IConfigurablePostProcessor.Config => Config;
+
         public CincinnatiPostProcessor()
         {
             var configPath = GetConfigPath();