Address claude-review round 5 on #919: - The "userinfo has no exp; caching for Ns only" log fired on every fresh userinfo validation (userinfo never returns exp) — downgrade WARNING → DEBUG; the bounded-staleness window is already documented on _validate_via_userinfo. - Add test_introspection_timeout_falls_through_to_userinfo: drives a real introspection timeout (httpx.TimeoutException on the POST, caught inside _introspect_token → None) through to a successful userinfo validation, pinning the documented error fall-through end to end. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>