refactor: 简化 AgentScope 运行时模块与事件处理

- 移除冗余的 user_token 参数传递
- 重构 tool.result 事件使用 ToolAgentOutput 模型
- 重构 text.end 事件使用 WorkerAgentOutput 模型
- 简化 store 模块的 tool result 处理逻辑
- 更新 router/service 适配新事件结构
- 清理废弃的测试文件与设计文档
- 新增 AgentRuns 多模态存储设计文档

backend/src/schemas/messages/chat_message.py

@@ -1,8 +1,11 @@
 from __future__ import annotations
 
+from datetime import datetime
+from decimal import Decimal
 from typing import ClassVar
+from uuid import UUID
 
-from pydantic import BaseModel, ConfigDict
+from pydantic import BaseModel, ConfigDict, Field
 
 from ..agent import AgentType, ToolAgentOutput, WorkerAgentOutput
 
@@ -22,3 +25,16 @@ class AgentChatMessageMetadata(BaseModel):
     user_message_attachments: UserMessageAttachments | None = None
     tool_agent_output: ToolAgentOutput | None = None
     worker_agent_output: WorkerAgentOutput | None = None
+
+
+class AgentChatMessage(BaseModel):
+    """Canonical schema aligned with `messages` table columns."""
+
+    model_config: ClassVar[ConfigDict] = ConfigDict(extra="forbid")
+
+    id: UUID
+    seq: int
+    role: str
+    content: str
+    metadata: AgentChatMessageMetadata | dict[str, object] | None = None
+    timestamp: datetime