test(agent-chat): audit guardrail and error handling

backend/src/agent/langgraph_setup.py

@@ -9,21 +9,6 @@
 # @REJECTED Using only environment variables for LLM config was rejected — FastAPI API-based config allows runtime switching without restart.
 #            RunnableWithMessageHistory wrapper is NOT used — PostgresSaver handles history natively.
 
-import os
-import time
-
-import httpx
-import psycopg
-from langchain_openai import ChatOpenAI
-from langgraph.checkpoint.memory import InMemorySaver
-from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
-from langgraph.prebuilt import create_react_agent
-from psycopg.rows import dict_row
-
-from src.agent._config import FASTAPI_URL, AGENT_CONFIRM_TOOLS, AGENT_INTERRUPT_BEFORE as _INTERRUPT_BEFORE
-from src.agent._llm_params import chat_openai_kwargs
-from src.core.logger import logger
-
 # ── Monkey-patch: OpenAI SDK for Pydantic BaseModel classes ──
 # LangChain BaseTool objects carry an ``args_schema`` field that is a Pydantic
 # BaseModel *class* reference (not an instance). When the OpenAI SDK recursively
@@ -34,12 +19,24 @@ from src.core.logger import logger
 #   PydanticSerializationError: Unable to serialize unknown type: ModelMetaclass
 #
 # The fix: skip model_dump for classes, only dump instances.
-
 import inspect as _inspect
+import os
+
+import httpx
+from langchain_openai import ChatOpenAI
+from langgraph.checkpoint.memory import InMemorySaver
+from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
+from langgraph.prebuilt import create_react_agent
 import openai._utils._transform as _openai_transform
+import psycopg
+from psycopg.rows import dict_row
 import pydantic as _pydantic
 import pydantic_core as _pydantic_core
 
+from src.agent._config import AGENT_CONFIRM_TOOLS, AGENT_INTERRUPT_BEFORE as _INTERRUPT_BEFORE, FASTAPI_URL
+from src.agent._llm_params import chat_openai_kwargs
+from src.core.logger import logger
+
 _original_transform = _openai_transform._async_transform_recursive
 
 async def _patched_transform(data, *, annotation, inner_type=None):