feat: AG-UI 协议对齐与路由导航功能

- 前端: 添加 SSE 流式支持、stateSnapshot 事件、路由导航工具
- 前端: 实现工具调用审批流程，支持 pending 状态展示
- 后端: Agent 状态管理与会话持久化相关重构
- 文档: 新增 agent-agui-full-alignance 设计文档
- 测试: 补充相关单元测试和集成测试

backend/src/v1/agent/repository.py

@@ -1,11 +1,14 @@
 from __future__ import annotations
 
+from datetime import date, datetime, time, timedelta, timezone
+import json
 from uuid import UUID
 
 from fastapi import HTTPException
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from models.agent_chat_message import AgentChatMessage, AgentChatMessageRole
 from models.agent_chat_session import AgentChatSession
 
 
@@ -27,13 +30,22 @@ class AgentRepository:
             raise HTTPException(status_code=404, detail="Session not found")
         return str(owner_id)
 
-    async def create_session_for_user(self, *, user_id: str) -> str:
+    async def create_session_for_user(
+        self, *, user_id: str, session_id: str | None = None
+    ) -> str:
         try:
             user_uuid = UUID(user_id)
         except ValueError as exc:
             raise HTTPException(status_code=422, detail="Invalid user_id") from exc
+        session_uuid = None
+        if session_id is not None:
+            try:
+                session_uuid = UUID(session_id)
+            except ValueError as exc:
+                raise HTTPException(status_code=422, detail="Invalid session_id") from exc
 
         session = AgentChatSession(
+            id=session_uuid,
             user_id=user_uuid,
         )
         self._session.add(session)
@@ -56,3 +68,114 @@ class AgentRepository:
         if session is not None:
             await self._session.delete(session)
             await self._session.flush()
+
+    async def get_history_day(
+        self, *, session_id: str, before: date | None
+    ) -> dict[str, object] | None:
+        try:
+            session_uuid = UUID(session_id)
+        except ValueError as exc:
+            raise HTTPException(status_code=422, detail="Invalid session_id") from exc
+
+        timestamp_stmt = (
+            select(AgentChatMessage.created_at)
+            .where(AgentChatMessage.session_id == session_uuid)
+            .where(AgentChatMessage.deleted_at.is_(None))
+            .order_by(AgentChatMessage.created_at.desc())
+        )
+        rows = (await self._session.execute(timestamp_stmt)).scalars().all()
+        unique_days: list[date] = []
+        for created_at in rows:
+            if created_at is None:
+                continue
+            day = created_at.astimezone(timezone.utc).date()
+            if day not in unique_days:
+                unique_days.append(day)
+
+        if not unique_days:
+            return None
+
+        target_day: date | None = None
+        if before is None:
+            target_day = unique_days[0]
+        else:
+            for day in unique_days:
+                if day < before:
+                    target_day = day
+                    break
+        if target_day is None:
+            return None
+
+        start = datetime.combine(target_day, time.min, tzinfo=timezone.utc)
+        end = start + timedelta(days=1)
+        message_stmt = (
+            select(AgentChatMessage)
+            .where(AgentChatMessage.session_id == session_uuid)
+            .where(AgentChatMessage.deleted_at.is_(None))
+            .where(AgentChatMessage.created_at >= start)
+            .where(AgentChatMessage.created_at < end)
+            .order_by(AgentChatMessage.seq.asc())
+        )
+        messages = (await self._session.execute(message_stmt)).scalars().all()
+        has_more = any(day < target_day for day in unique_days)
+        return {
+            "day": target_day.isoformat(),
+            "hasMore": has_more,
+            "messages": [self._to_snapshot_message(msg) for msg in messages],
+        }
+
+    async def get_latest_session_id_for_user(self, *, user_id: str) -> str | None:
+        try:
+            user_uuid = UUID(user_id)
+        except ValueError as exc:
+            raise HTTPException(status_code=422, detail="Invalid user_id") from exc
+        stmt = (
+            select(AgentChatSession.id)
+            .where(AgentChatSession.user_id == user_uuid)
+            .where(AgentChatSession.deleted_at.is_(None))
+            .order_by(AgentChatSession.last_activity_at.desc())
+            .limit(1)
+        )
+        latest_id = (await self._session.execute(stmt)).scalar_one_or_none()
+        if latest_id is None:
+            return None
+        return str(latest_id)
+
+    @staticmethod
+    def _to_snapshot_message(message: AgentChatMessage) -> dict[str, object]:
+        role = (
+            message.role.value
+            if isinstance(message.role, AgentChatMessageRole)
+            else str(message.role)
+        )
+        payload: dict[str, object] = {
+            "id": str(message.id),
+            "role": role,
+            "timestamp": message.created_at.astimezone(timezone.utc).isoformat(),
+        }
+
+        if role == AgentChatMessageRole.TOOL.value:
+            metadata = message.metadata_json or {}
+            tool_call_id = metadata.get("tool_call_id")
+            if isinstance(tool_call_id, str) and tool_call_id:
+                payload["toolCallId"] = tool_call_id
+
+            parsed_content: dict[str, object] | None = None
+            try:
+                decoded = json.loads(message.content)
+                if isinstance(decoded, dict):
+                    parsed_content = decoded
+            except (TypeError, ValueError):
+                parsed_content = None
+            if parsed_content is not None:
+                ui = parsed_content.get("ui")
+                if isinstance(ui, dict):
+                    payload["ui"] = ui
+                display_content = parsed_content.get("content")
+                if isinstance(display_content, str):
+                    payload["content"] = display_content
+            else:
+                payload["content"] = message.content
+        else:
+            payload["content"] = message.content
+        return payload