docs(setting): 添加设置系统文档并实现JSON序列化器

- 新增设置系统详细文档，包含核心概念、接口定义和基本用法
- 实现JSON序列化器支持对象序列化和反序列化功能
- 添加序列化器单元测试验证序列化功能正确性
- 提供自定义转换器支持和错误处理机制

GFramework.Game.Tests/Serializer/JsonSerializerTests.cs

@@ -93,6 +93,26 @@ public sealed class JsonSerializerTests
         Assert.That(((PlayerStateStub)restored).Level, Is.EqualTo(11));
     }
 
+    [Test]
+    public void Serialize_With_Runtime_Type_Should_Allow_Null_Object()
+    {
+        var serializer = new GameJsonSerializer();
+
+        var json = serializer.Serialize(null!, typeof(PlayerStateStub));
+
+        Assert.That(json, Is.EqualTo("null"));
+    }
+
+    [Test]
+    public void Deserialize_Should_Preserve_ArgumentException_For_Invalid_Input_Arguments()
+    {
+        var serializer = new GameJsonSerializer();
+
+        var exception = Assert.Throws<ArgumentException>(() => serializer.Deserialize<PlayerStateStub>(string.Empty));
+
+        Assert.That(exception, Is.Not.Null);
+    }
+
     private sealed class PlayerStateStub
     {
         public string Name { get; set; } = string.Empty;
@@ -121,7 +141,7 @@ public sealed class JsonSerializerTests
             writer.WriteValue($"{value?.X}:{value?.Y}");
         }
 
-        public override CoordinateStub? ReadJson(
+        public override CoordinateStub ReadJson(
             JsonReader reader,
             Type objectType,
             CoordinateStub? existingValue,

GFramework.Game/Serializer/JsonSerializer.cs

@@ -1,6 +1,5 @@
 using GFramework.Core.Abstractions.Serializer;
 using Newtonsoft.Json;
-using NewtonsoftJsonException = Newtonsoft.Json.JsonException;
 
 namespace GFramework.Game.Serializer;
 
@@ -51,7 +50,6 @@ public sealed class JsonSerializer
     /// <returns>序列化后的JSON字符串</returns>
     public string Serialize(object obj, Type type)
     {
-        ArgumentNullException.ThrowIfNull(obj);
         ArgumentNullException.ThrowIfNull(type);
 
         return JsonConvert.SerializeObject(obj, type, _settings);
@@ -107,7 +105,7 @@ public sealed class JsonSerializer
 
             return result;
         }
-        catch (Exception ex) when (ex is NewtonsoftJsonException or InvalidCastException or ArgumentException)
+        catch (Exception ex) when (ex is InvalidCastException)
         {
             throw new InvalidOperationException(
                 $"Failed to deserialize JSON to target type '{targetType.FullName}'.",

docs/zh-CN/game/setting.md

@@ -175,7 +175,7 @@ public interface ISettingsMigration
     Type SettingsType { get; }
     int FromVersion { get; }
     int ToVersion { get; }
-    ISettingsSection Migrate(ISettingsSection oldData);
+    ISettingsData Migrate(ISettingsData oldData);
 }
 ```