Add GET / -> /demo/ redirect for Space iframe

HF Spaces iframes load the Space URL root, but our FastAPI app only
defined endpoint routes. Visitors saw FastAPI's stock {detail: Not Found}.
Redirect / to /demo/ so the Gradio "before vs after" UI is what humans
land on; the JSON API surface (/health, /reset, /step, /grade, /tasks)
is unchanged for OpenEnv judges.

Made-with: Cursor

app_runtime.py

@@ -27,6 +27,7 @@ from typing import Any, Dict, Optional
 
 from fastapi import FastAPI, HTTPException, Query
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import RedirectResponse
 from pydantic import BaseModel
 
 from env import Action, Observation, OpenSOCEnv
@@ -169,6 +170,13 @@ def health():
     return {"status": "ok", "env": "OpenSOC", "version": "1.0.0"}
 
 
+@app.get("/", include_in_schema=False)
+def index():
+    # Spaces iframes load the root URL; send human visitors to the Gradio
+    # demo and leave the JSON API endpoints untouched for the OpenEnv judge.
+    return RedirectResponse(url="/demo/", status_code=307)
+
+
 def main() -> None:
     import uvicorn