新增 scene.signal 信号交互插件，落地 PLC 握手与扫车放行。

Co-authored-by: Cursor <cursoragent@cursor.com>

StandardScene.Signal/Logic/SignalStopSpec.cs

@@ -0,0 +1,42 @@
+using System;
+using StandardScene.Signal.Model;
+
+namespace StandardScene.Signal.Logic
+{
+    /// <summary>握手点解析结果。参数格式与反编译 SignalStop.SignalParams 一致。</summary>
+    public sealed class SignalStopSpec
+    {
+        public string SignalType { get; init; } = "";
+        public string SignalParams { get; init; } = "";
+        public string[] Parts { get; init; } = Array.Empty<string>();
+
+        public string Part(int index)
+        {
+            if (index < 0 || index >= Parts.Length)
+                return "";
+            return Parts[index] ?? "";
+        }
+
+        public static SignalStopSpec Parse(string signalType, string signalParams)
+        {
+            var type = (signalType ?? "").Trim();
+            var raw = signalParams ?? "";
+            return new SignalStopSpec
+            {
+                SignalType = type,
+                SignalParams = raw,
+                Parts = raw.Split(new[] { ';' }, StringSplitOptions.None)
+            };
+        }
+
+        public static SignalStopSpec From(HandshakePointModel model)
+        {
+            if (model == null)
+                return null;
+            return Parse(model.SignalType, model.SignalParams);
+        }
+
+        public bool Is(string type) =>
+            string.Equals(SignalType, type, StringComparison.OrdinalIgnoreCase);
+    }
+}