refactor: Remove unused CompatibleGrainSerializer, focus on Orleans compatibility only

- Remove CompatibleGrainSerializer and related configuration methods
- Remove CompatibilityTests.cs and related test methods
- Keep only OrleansCompatibleGrainSerializer for Orleans LogStateWithMetaData support
- Simplify codebase to focus on actual use case (Orleans → MongoDB migration)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: louis4li

src/Aevatar.EventSourcing.MongoDB/Hosting/MongoDbStorageServiceCollectionExtensions.cs

@@ -87,43 +87,6 @@ public static IServiceCollection AddMongoDbBasedLogConsistencyProvider(this ISer
         return services;
     }
 
-    /// <summary>
-    /// Adds MongoDB-based log consistency provider with backward compatibility for Memory storage format
-    /// </summary>
-    public static IServiceCollection AddCompatibleMongoDbBasedLogConsistencyProvider(this IServiceCollection services,
-        string name, Action<OptionsBuilder<MongoDbStorageOptions>>? configureOptions = null)
-    {
-        // Register the compatible serializer
-        services.AddKeyedSingleton<IGrainStateSerializer>(name, (sp, key) => new CompatibleGrainSerializer());
-        
-        // Use the standard MongoDB provider setup
-        return services.AddMongoDbBasedLogConsistencyProvider(name, configureOptions);
-    }
-
-    /// <summary>
-    /// Adds MongoDB-based log consistency provider as default with backward compatibility for Memory storage format
-    /// </summary>
-    public static IServiceCollection AddCompatibleMongoDbBasedLogConsistencyProviderAsDefault(this IServiceCollection services,
-        Action<OptionsBuilder<MongoDbStorageOptions>>? configureOptions = null)
-    {
-        return services.AddCompatibleMongoDbBasedLogConsistencyProvider(
-            ProviderConstants.DEFAULT_STORAGE_PROVIDER_NAME, configureOptions);
-    }
-
-    /// <summary>
-    /// Adds MongoDB-based log consistency provider with backward compatibility and custom serializer configuration
-    /// </summary>
-    public static IServiceCollection AddCompatibleMongoDbBasedLogConsistencyProvider(this IServiceCollection services,
-        string name, Action<MongoDbStorageOptions> configureOptions, bool useCompatibleSerializer = true)
-    {
-        if (useCompatibleSerializer)
-        {
-            // Register the compatible serializer
-            services.AddKeyedSingleton<IGrainStateSerializer>(name, (sp, key) => new CompatibleGrainSerializer());
-        }
-        
-        return services.AddMongoDbBasedLogConsistencyProvider(name, configureOptions);
-    }
 
 
     /// <summary>

src/Aevatar.EventSourcing.MongoDB/Serializers/CompatibleGrainSerializer.cs

@@ -67,27 +67,6 @@ public void OrleansCompatibleGrainSerializer_CanHandleSimpleJsonFormat()
         Assert.NotNull(result);
     }
 
-    [Fact]
-    public void CompatibleGrainSerializer_CanDeserializeRealMemoryFormat()
-    {
-        // Arrange - 使用原始的兼容序列化器测试简单格式
-        var simpleJson = """
-        {
-            "PromptTemplate": "Test prompt template",
-            "Id": "00000000-0000-0000-0000-000000000000",
-            "Ctime": "0001-01-01T00:00:00"
-        }
-        """;
-
-        var bsonString = new BsonString(simpleJson);
-        var serializer = new CompatibleGrainSerializer();
-
-        // Act
-        var result = serializer.Deserialize<object>(bsonString);
-
-        // Assert
-        Assert.NotNull(result);
-    }
 
     [Fact]
     public void TestComplexTypeDeserialization()