13-sso proves an authenticated session reaches Grafana login page but never
follows the OAuth button, so the relying-party login could be dead (500, or an
email-claim gap bouncing to /login) while the suite stayed green. Spec 20 drives
/login/generic_oauth through the real Anubis+authentik round-trip and asserts a
live session (/api/user 200 with a non-empty email). Wire 20- into the standard
project (qa-e2e session).