refactor(posts): move post-processor projects under Posts/

Group the Cincinnati and GravographIS plugin projects in a Posts/
folder so new machine posts have one home. Project names, namespaces,
and the runtime Posts/ deploy target are unchanged; only relative
paths in the solution and project references move.

Posts/OpenNest.Posts.GravographIS/GravographISPostProcessor.cs

@@ -0,0 +1,169 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.IO.Ports;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Threading;
+using OpenNest.Geometry;
+
+namespace OpenNest.Posts.GravographIS
+{
+    /// <summary>
+    /// IPostProcessor implementation for the Gravograph IS8000. <see cref="Post(Nest, Stream)"/>
+    /// writes the binary HPGL bytes. For serial streaming, use <see cref="Stream(Nest, string, Handshake, CancellationToken)"/>.
+    ///
+    /// Geometry is split by <see cref="OpenNest.CNC.LayerType"/> into an engrave pass
+    /// (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
+    {
+        private static readonly JsonSerializerOptions JsonOptions = new()
+        {
+            WriteIndented = true,
+            Converters = { new JsonStringEnumConverter() },
+        };
+
+        public string Name => "Gravograph IS8000";
+        public string Author => "OpenNest";
+        public string Description =>
+            "Gravograph IS8000 mechanical engraver (binary HPGL over serial)";
+
+        public GravographISWriterOptions WriterOptions { get; } = new GravographISWriterOptions();
+
+        public NestPolylineExtractor Extractor { get; } = new NestPolylineExtractor();
+
+        public double StitchTolerance { get; set; } = PolylinePrePass.DefaultStitchTolerance;
+
+        public bool AllowReverse { get; set; } = true;
+
+        public GravographISPostConfig Config { get; }
+
+        object IConfigurablePostProcessor.Config => Config;
+
+        public GravographISPostProcessor()
+        {
+            var configPath = GetConfigPath();
+            if (File.Exists(configPath))
+            {
+                var json = File.ReadAllText(configPath);
+                Config =
+                    JsonSerializer.Deserialize<GravographISPostConfig>(json, JsonOptions)
+                    ?? new GravographISPostConfig();
+            }
+            else
+            {
+                Config = new GravographISPostConfig();
+                SaveConfig();
+            }
+        }
+
+        public GravographISPostProcessor(GravographISPostConfig 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(GravographISPostProcessor).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));
+
+            var passes = BuildPasses(Extractor.ExtractLayered(nest));
+            new GravographISWriter(WriterOptions).Write(passes, outputStream);
+        }
+
+        public void Post(Nest nest, string outputFile)
+        {
+            using var fs = new FileStream(outputFile, FileMode.Create, FileAccess.Write);
+            Post(nest, fs);
+        }
+
+        /// <summary>
+        /// Groups layer-tagged polylines into ordered tool passes: engrave (Scribe)
+        /// first, then cut. Each group is stitch/reverse-optimized independently.
+        /// Geometry whose layer maps to no config (Display) is skipped. When only one
+        /// group is present, a single pass is returned (and so the writer emits no pause).
+        /// </summary>
+        public IReadOnlyList<GravographPass> BuildPasses(IEnumerable<LayeredPolyline> polylines)
+        {
+            if (polylines == null)
+                throw new ArgumentNullException(nameof(polylines));
+
+            var engrave = new List<IReadOnlyList<Vector>>();
+            var cut = new List<IReadOnlyList<Vector>>();
+
+            foreach (var poly in polylines)
+            {
+                if (poly == null)
+                    continue;
+                var block = Config.ConfigFor(poly.Layer);
+                if (block == null)
+                    continue; // non-cutting (Display) geometry
+                if (ReferenceEquals(block, Config.Engrave))
+                    engrave.Add(poly.Points);
+                else
+                    cut.Add(poly.Points);
+            }
+
+            var passes = new List<GravographPass>();
+            if (engrave.Count > 0)
+                passes.Add(MakePass(Config.Engrave, engrave));
+            if (cut.Count > 0)
+                passes.Add(MakePass(Config.Cut, cut));
+
+            return passes;
+        }
+
+        private GravographPass MakePass(LayerCutConfig block, List<IReadOnlyList<Vector>> polylines)
+        {
+            return new GravographPass
+            {
+                Polylines = PolylinePrePass.Prepare(polylines, StitchTolerance, AllowReverse),
+                FeedMmPerSec = block.FeedMmPerSec,
+                DepthInches = block.Depth,
+                PauseBefore = block.PauseBefore,
+                PauseMessage = block.PauseMessage ?? "",
+            };
+        }
+
+        /// <summary>
+        /// Buffers the encoded job in memory, then streams it to the named COM port.
+        /// </summary>
+        public void Stream(
+            Nest nest,
+            string portName,
+            Handshake handshake = Handshake.RequestToSend,
+            CancellationToken cancellationToken = default
+        )
+        {
+            byte[] bytes;
+            using (var ms = new MemoryStream())
+            {
+                Post(nest, ms);
+                bytes = ms.ToArray();
+            }
+
+            using var port = new GravographISPort();
+            port.Open(portName, handshake);
+            port.StreamJob(bytes, cancellationToken);
+        }
+    }
+}