feat(objects): ObjectCacheGenerator core + GenObjects command

Wraps introspection, categorization sync, and cache-building into a
single file-I/O-free Generate() so the full pipeline is testable
without a shard; GenObjects is a thin command that adds file I/O and
operator messaging on top.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Projects/UOContent.Tests/Tests/Commands/Objects/ObjectCacheGeneratorTests.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using Server.Commands;
+using Server.Items;
+using Xunit;
+
+namespace UOContent.Tests.Commands.Objects;
+
+[Collection("Sequential UOContent Tests")]
+public class ObjectCacheGeneratorTests
+{
+    [Fact]
+    public void Generate_builds_index_and_chunks_from_extracted_objects()
+    {
+        var discovered = new List<Type> { typeof(Runebook), typeof(Katana) };
+        var categorization = new List<CAGJson>(); // empty -> both land in Items.Uncategorized
+
+        var result = ObjectCacheGenerator.Generate(categorization, discovered);
+
+        Assert.Equal(2, result.Index.Objects.Count);
+        Assert.NotEmpty(result.Chunks);
+
+        var runebook = Assert.Single(result.Index.Objects, o => o.Type == "Runebook");
+        Assert.True(runebook.ItemID > 0);
+        Assert.Equal(1041267, runebook.Cliloc);
+        Assert.Equal("items.uncategorized", runebook.Chunk);
+
+        Assert.Contains("Runebook", result.Report.Appended);
+        Assert.Contains("items.uncategorized", result.Chunks.Keys);
+        Assert.Contains("Runebook", result.Chunks["items.uncategorized"].Keys);
+    }
+}