Delete the in-tree cache, JsonKnownTypes and vendored MessagePack

Cut 8b, deletes first. The old authorities are removed, not demoted:
- ServerShared/CultCache: CultCache.cs, DatabaseEntry.cs (root [Union],
  DatabaseLink, INamedEntry), RegisterResolver.cs, TypeFormatterResolver.cs,
  JsonConverters.cs, JsonKnownTypes/**.
- Assets/Plugins/MessagePack/** and System.Runtime.CompilerServices.Unsafe.dll
  (org.gamecult.cultlib ships both).
- GalaxyMapLayerData, PlayerData, GlobalSettingsAttribute.
- The inspector attributes CultLib already carries or nothing reads.

Kept and moved: MathFormatters.cs and MathResolver.cs to
ServerShared/Serialization; GetAllChildClasses, SplitCamelCase,
FormatTypeName, MaxBy and MinBy to Extensions.cs; Inspectable,
PreferredInspectorAttribute and the five Aetheria drawer attributes to
ServerShared/Attributes.cs. Aetheria.Shared.csproj drops the vendored
MessagePack include and the Unsafe package; the asmdef drops MessagePack.

Does not build: the data model moves onto CultLib in the next commit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/Serialization/MathResolver.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using MessagePack;
+using MessagePack.Formatters;
+using CultMath;
+using static CultMath.math;
+
+
+public class MathResolver : IFormatterResolver
+{
+    public static readonly MathResolver Instance = new MathResolver();
+
+    private MathResolver()
+    {
+    }
+
+    public IMessagePackFormatter<T> GetFormatter<T>()
+    {
+        return FormatterCache<T>.Formatter;
+    }
+
+    private static class FormatterCache<T>
+    {
+        public static readonly IMessagePackFormatter<T> Formatter;
+
+        static FormatterCache()
+        {
+            Formatter = (IMessagePackFormatter<T>)MathResolverResolverGetFormatterHelper.GetFormatter(typeof(T));
+        }
+    }
+}
+
+internal static class MathResolverResolverGetFormatterHelper
+{
+    private static readonly Dictionary<Type, object> FormatterMap = new Dictionary<Type, object>()
+    {
+        // standard
+        { typeof(float2), new Float2Formatter() },
+        { typeof(int2), new Int2Formatter() },
+        { typeof(bool2), new Bool2Formatter() },
+        { typeof(float3), new Float3Formatter() },
+        { typeof(float4), new Float4Formatter() },
+        { typeof(float2?), new StaticNullableFormatter<float2>(new Float2Formatter()) },
+        { typeof(int2?), new StaticNullableFormatter<int2>(new Int2Formatter()) },
+        { typeof(float3?), new StaticNullableFormatter<float3>(new Float3Formatter()) },
+        { typeof(float4?), new StaticNullableFormatter<float4>(new Float4Formatter()) },
+
+        // standard + array
+        { typeof(float2[]), new ArrayFormatter<float2>() },
+        { typeof(int2[]), new ArrayFormatter<int2>() },
+        { typeof(float3[]), new ArrayFormatter<float3>() },
+        { typeof(float4[]), new ArrayFormatter<float4>() },
+        { typeof(float2?[]), new ArrayFormatter<float2?>() },
+        { typeof(int2?[]), new ArrayFormatter<int2?>() },
+        { typeof(float3?[]), new ArrayFormatter<float3?>() },
+        { typeof(float4?[]), new ArrayFormatter<float4?>() },
+
+        // standard + list
+        { typeof(List<float2>), new ListFormatter<float2>() },
+        { typeof(List<int2>), new ListFormatter<int2>() },
+        { typeof(List<float3>), new ListFormatter<float3>() },
+        { typeof(List<float4>), new ListFormatter<float4>() },
+        { typeof(List<float2?>), new ListFormatter<float2?>() },
+        { typeof(List<int2?>), new ListFormatter<int2?>() },
+        { typeof(List<float3?>), new ListFormatter<float3?>() },
+        { typeof(List<float4?>), new ListFormatter<float4?>() },
+    };
+
+    internal static object GetFormatter(Type t)
+    {
+        object formatter;
+        if (FormatterMap.TryGetValue(t, out formatter))
+        {
+            return formatter;
+        }
+
+        return null;
+    }
+}