auth_bruteforce
Username enumeration and credential brute-force.
First enumerates valid usernames (if failure messages differ), then brute-forces passwords against confirmed usernames.
Returns: {"username_enumeration": [{"username": str, "exists": bool}], "valid_credentials": [{"username": str, "password": str}], "requests_sent": int}.
Side effects: Sends login requests. May trigger account lockout.
Errors: Rate limiting may block requests. Use realistic credentials to avoid WAF detection.