Fix /reset to accept empty POST body

Make the reset request body optional so OpenEnv automation that posts without a JSON payload no longer fails with 422 'Field required'. Keep existing behavior unchanged when a body is provided.

Made-with: Cursor

app.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 from pathlib import Path
 from typing import Any
 
-from fastapi import FastAPI, HTTPException
+from fastapi import Body, FastAPI, HTTPException
 from fastapi.responses import PlainTextResponse
 from pydantic import BaseModel, Field
 
@@ -67,7 +67,8 @@ def tasks() -> list[dict[str, Any]]:
 
 
 @app.post("/reset")
-def reset(request: ResetRequest) -> dict[str, Any]:
+def reset(request: ResetRequest | None = Body(default=None)) -> dict[str, Any]:
+    request = request or ResetRequest()
     env = EmailTriageEnv(task_id=request.task_id, seed=request.seed)
     _sessions[request.session_id] = env
     observation = env.reset(scenario_id=request.scenario_id)