整理配置和代码入口，增加部分测试。

sync_state_machine/common/registry.py

@@ -26,7 +26,7 @@ Domain 注册中心
     # DataSource 查询 Handler
     handler_class = DomainRegistry.get_jsonl_handler("contract")
 """
-from typing import Dict, Type, Optional, Any
+from typing import Dict, Type, Optional, Any, Literal
 from dataclasses import dataclass, field
 from pydantic import BaseModel
 
@@ -64,6 +64,12 @@ class DomainRegistry:
     """
     
     _registry: Dict[str, DomainRegistration] = {}
+
+    _HANDLER_ATTRS: Dict[str, str] = {
+        "jsonl": "jsonl_handler_class",
+        "api": "api_handler_class",
+        "db": "db_handler_class",
+    }
     
     @classmethod
     def register(
@@ -143,36 +149,30 @@ class DomainRegistry:
         return reg.strategy_class
     
     @classmethod
-    def get_jsonl_handler(cls, node_type: str) -> Optional[Type[Any]]:
-        """
-        获取 JSONL Handler 类（用于 DataSource）
-        
-        Args:
-            node_type: 节点类型
-            
-        Returns:
-            Handler 类，如果未注册则返回 None
-        """
+    def get_handler(
+        cls,
+        node_type: str,
+        datasource_type: Literal["jsonl", "api", "db"],
+    ) -> Optional[Type[Any]]:
+        """按 datasource 类型获取 Handler 类。"""
         reg = cls._registry.get(node_type)
         if not reg:
             raise ValueError(f"Unknown node_type: '{node_type}'")
-        return reg.jsonl_handler_class
-    
+        attr_name = cls._HANDLER_ATTRS.get(datasource_type)
+        if attr_name is None:
+            raise ValueError(
+                f"Unsupported datasource_type: '{datasource_type}'. "
+                f"Available: {sorted(cls._HANDLER_ATTRS.keys())}"
+            )
+        return getattr(reg, attr_name)
+
     @classmethod
-    def get_api_handler(cls, node_type: str) -> Optional[Type[Any]]:
-        """获取 API Handler 类"""
+    def register_db_handler(cls, node_type: str, db_handler_class: Type[Any]) -> None:
+        """为已注册 domain 补充 DB Handler。"""
         reg = cls._registry.get(node_type)
         if not reg:
             raise ValueError(f"Unknown node_type: '{node_type}'")
-        return reg.api_handler_class
-    
-    @classmethod
-    def get_db_handler(cls, node_type: str) -> Optional[Type[Any]]:
-        """获取 DB Handler 类"""
-        reg = cls._registry.get(node_type)
-        if not reg:
-            raise ValueError(f"Unknown node_type: '{node_type}'")
-        return reg.db_handler_class
+        reg.db_handler_class = db_handler_class
     
     @classmethod
     def get_schema(cls, node_type: str) -> Type[BaseModel]: