feat: 添加 tool_call_history, stop, tools_used 等新状态字段

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/app/main_graph/state.py

@@ -9,7 +9,7 @@
 - 统计：llm_calls, last_token_usage, last_elapsed_time
 """
 
-from typing import Annotated, Sequence, Optional, Dict, Any
+from typing import Annotated, Sequence, Optional, Dict, Any, List
 from dataclasses import dataclass, field
 from langgraph.graph import add_messages
 from langchain_core.messages import BaseMessage
@@ -35,3 +35,14 @@ class AgentState:
     llm_calls: int = 0
     last_token_usage: Dict[str, Any] = field(default_factory=dict)
     last_elapsed_time: float = 0.0
+
+    # ========== 新增字段: 工具调用历史 ==========
+    tool_call_history: List[dict] = field(default_factory=list)
+    tool_result_history: List[str] = field(default_factory=list)
+
+    # ========== 新增字段: 停止控制 ==========
+    stop: bool = False
+    stop_reason: str = ""
+
+    # ========== 新增字段: 本轮使用的工具 ==========
+    tools_used: List[str] = field(default_factory=list)