Schema model: catalog, field types, references, checker and line writer shared by tools and validator

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

tests/SchemaReferencesTests.cs

@@ -0,0 +1,26 @@
+namespace Cthangover.Mods.Schemas.Tests
+{
+    using System.Linq;
+    using Cthangover.Core.Mods.Testing;
+
+    /// <summary>Which entity references a value makes, by its field type.</summary>
+    public class SchemaReferencesTests
+    {
+        private static string Refs(FieldSchema field, string value)
+            => string.Join(";", SchemaReferences.Of(field, value).Select(r => r.Kind + ":" + r.Id));
+
+        [ModTest("references/by_type")]
+        static void ByType(ModTestContext ctx)
+        {
+            ModAssert.Equal("item:sword", Refs(new FieldSchema { Type = "ref", Kind = "item" }, " sword "), "ref");
+            ModAssert.Equal("character:a;character:b", Refs(new FieldSchema { Type = "ref_list", Kind = "character" }, "a, b,"), "ref_list");
+            ModAssert.Equal("character:hero", Refs(new FieldSchema { Type = "who" }, "hero"), "who names a character");
+            ModAssert.Equal("", Refs(new FieldSchema { Type = "who" }, "party"), "party is no reference");
+            ModAssert.Equal("", Refs(new FieldSchema { Type = "who" }, "Player"), "player is no reference");
+            ModAssert.Equal("scene:town", Refs(new FieldSchema { Type = "scene" }, "town"), "scene");
+            ModAssert.Equal("", Refs(new FieldSchema { Type = "text" }, "anything"), "text makes none");
+            ModAssert.Equal("", Refs(new FieldSchema { Type = "ref" }, "x"), "a ref without a kind makes none");
+            ModAssert.Equal("", Refs(new FieldSchema { Type = "ref", Kind = "item" }, "${picked}"), "a run-time value makes none");
+        }
+    }
+}