feat(posts): add Cincinnati CI Fiber (TF5200) post-processor

New post-processor plugin OpenNest.Posts.CincinnatiCIFiber for the CI
Fiber laser family (nLight CLX / Beckhoff TF5200 / Precitec ProCutter,
e.g. the CI Fiber 4020 8kW). Named by machine family, not table size.

Emits the machine program contract of the Cincinnati-supplied sample NC
(12992-4SS_NEST.nc): V.E.* header, restart jump, per-part V.E.R4 blocks,
per-contour N labels with V.E.R3, skippable /L macro lines (L0/L2+G41
interior, L4+G42 exterior, L6 cut-on, ZHSOFF cut-end), G162 incremental
arc I/J, trimmed 3-decimal spaceless coordinates, CRLF, M50/M30/%.

Contour classification (interior vs exterior) derives from the material
side of the closed cut path, not hardcoded winding. SubProgramCall holes
are flattened to sheet coordinates (rotation-safe). Arc lead-ins are
rejected per TF5200 13.2.4.1 (first motion block after G41/G42 selection
must be linear). Table envelope (default 160.25 x 81.25 in) validated.

Tests: structure golden on a square-with-hole nest, rotated-hole flatten,
coordinate format, arc-lead-in rejection, table validation, suppressed/
scribe skipping, plus a SkippableFact regression against the real sample
NC (109 parts, 2071 contours, L2=1962, L4=109, perimeter vertices match
within 0.001). Fixtures configure through OpenNest.Tests/test-config.json
and the regression skips when absent.

Posts/OpenNest.Posts.CincinnatiCIFiber/CIFiberPostProcessor.cs

@@ -0,0 +1,102 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using OpenNest.CNC;
+
+namespace OpenNest.Posts.CincinnatiCIFiber
+{
+    /// <summary>
+    /// Post-processor for the CI Fiber family (e.g. the CI Fiber 4020 8kW with
+    /// nLight CLX / Beckhoff TF5200 / Precitec ProCutter). Named by machine
+    /// family, not table size: the same post drives other CI Fiber tables via
+    /// the configured table envelope. Emits the TF5200 skippable-macro program
+    /// structure of the machine sample (see <see cref="CIFiberProgramWriter"/>).
+    /// </summary>
+    public sealed class CIFiberPostProcessor : IConfigurablePostProcessor
+    {
+        private static readonly JsonSerializerOptions JsonOptions = new()
+        {
+            WriteIndented = true,
+            Converters = { new JsonStringEnumConverter() },
+        };
+
+        public string Name => "Cincinnati CI Fiber";
+        public string Author => "OpenNest";
+        public string Description =>
+            "CI Fiber family laser (TF5200 / nLight CLX), e.g. CI Fiber 4020 8kW";
+
+        public CIFiberPostConfig Config { get; }
+
+        object IConfigurablePostProcessor.Config => Config;
+
+        public CIFiberPostProcessor()
+        {
+            var configPath = GetConfigPath();
+            if (File.Exists(configPath))
+            {
+                var json = File.ReadAllText(configPath);
+                Config =
+                    JsonSerializer.Deserialize<CIFiberPostConfig>(json, JsonOptions)
+                    ?? new CIFiberPostConfig();
+            }
+            else
+            {
+                Config = new CIFiberPostConfig();
+                SaveConfig();
+            }
+        }
+
+        public CIFiberPostProcessor(CIFiberPostConfig config)
+        {
+            Config = config ?? throw new ArgumentNullException(nameof(config));
+        }
+
+        public void SaveConfig()
+        {
+            var configPath = GetConfigPath();
+            var json = JsonSerializer.Serialize(Config, JsonOptions);
+            File.WriteAllText(configPath, json);
+        }
+
+        private static string GetConfigPath()
+        {
+            var assemblyPath = typeof(CIFiberPostProcessor).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)
+        {
+            if (nest == null)
+                throw new ArgumentNullException(nameof(nest));
+            if (outputStream == null)
+                throw new ArgumentNullException(nameof(outputStream));
+
+            // CRLF file, ASCII (UTF-8 without BOM), matching the machine sample.
+            var encoding = new UTF8Encoding(false);
+            using var writer = new StreamWriter(
+                outputStream,
+                encoding,
+                1024,
+                leaveOpen: true
+            );
+            new CIFiberProgramWriter(Config).Write(nest, writer);
+            writer.Flush();
+        }
+
+        public void Post(Nest nest, string outputFile)
+        {
+            using var fs = new FileStream(
+                outputFile,
+                FileMode.Create,
+                FileAccess.Write
+            );
+            Post(nest, fs);
+        }
+    }
+}