fix: resumable shell, works w/ interrupts (#33978)
fixes https://github.com/langchain-ai/langchain/issues/33684
Now able to run this minimal snippet successfully
```py
import os
from langchain.agents import create_agent
from langchain.agents.middleware import (
HostExecutionPolicy,
HumanInTheLoopMiddleware,
ShellToolMiddleware,
)
from langgraph.checkpoint.memory import InMemorySaver
from langgraph.types import Command
shell_middleware = ShellToolMiddleware(
workspace_root=os.getcwd(),
env=os.environ, # danger
execution_policy=HostExecutionPolicy()
)
hil_middleware = HumanInTheLoopMiddleware(interrupt_on={"shell": True})
checkpointer = InMemorySaver()
agent = create_agent(
"openai:gpt-4.1-mini",
middleware=[shell_middleware, hil_middleware],
checkpointer=checkpointer,
)
input_message = {"role": "user", "content": "run `which python`"}
config = {"configurable": {"thread_id": "1"}}
result = agent.invoke(
{"messages": [input_message]},
config=config,
durability="exit",
)
```
