refactor: 重构 AgentScope ReAct Runner 与事件处理

- 重构 runtime/runner.py 实现 ReAct Agent 核心逻辑
- 更新事件编码器与存储机制
- 优化 prompt 系统与 tool 调用
- 调整 agent service 与 repository 配合

backend/src/v1/agent/service.py

@@ -170,12 +170,9 @@ class AgentService:
             command={
                 "command": "run",
                 "owner_id": str(current_user.id),
-                "run_input": {
-                    "messages": [
-                        msg.model_dump(mode="json", exclude_none=True)
-                        for msg in run_input.messages
-                    ],
-                },
+                "run_input": run_input.model_dump(
+                    mode="json", by_alias=True, exclude_none=True
+                ),
             },
             dedup_key=None,
         )
@@ -204,7 +201,7 @@ class AgentService:
 
         yesterday = await self._repository.get_history_day(
             session_id=thread_id,
-            before=today.get("day"),  # type: ignore
+            before=self._parse_history_day(today.get("day")),
         )
 
         messages: list[dict[str, object]] = []
@@ -215,6 +212,16 @@ class AgentService:
 
         return {"messages": messages}
 
+    def _parse_history_day(self, value: object) -> date | None:
+        if isinstance(value, date):
+            return value
+        if isinstance(value, str):
+            try:
+                return date.fromisoformat(value)
+            except ValueError:
+                return None
+        return None
+
     async def _prepare_user_message(
         self,
         *,