Non-JSON responses and read timeouts escape as JSONDecodeError / TimeoutError instead of RouterError

[TheCoder30ec4]

Problem

request_json in src/model_router/_http.py only converts HTTPError and URLError into RouterError. Two other common failures leak out as different exception types:

Situation	What route() raises today
Server answers 200 with a non-JSON body (proxy / CDN error page)	json.JSONDecodeError
Connection opens, then the response read times out	TimeoutError

The README tells users to write except RouterError: and fall back to a default model (see "Using it in an agent"). With these leaks, that fallback never runs and the agent crashes instead.

Reproduce

import io
from unittest.mock import MagicMock, patch
from model_router._http import request_json

resp = MagicMock()
resp.__enter__.return_value = io.BytesIO(b"<html>oops</html>")
with patch("urllib.request.urlopen", return_value=resp):
    request_json("https://x.test")  # json.JSONDecodeError, expected RouterError

Suggested fix

In request_json, also catch json.JSONDecodeError and TimeoutError (plus OSError for connection resets) and re-raise as RouterError(...) from e. Keep the original exception chained.

Done when

• Both cases above raise RouterError
• Tests added in tests/test_http.py