The logged-out landing probed /api/me, which 401'd, and the browser logs every
non-2xx fetch as a console error regardless of how the app handles it. The
bootstrap probe now returns 200 with {authenticated:false} via a new
optional_current_user dependency; api.me() maps that to null. The render gate
treats no-data as 'signed out' -> the landing, and a thrown error as a real
network/5xx failure. Other protected endpoints still 401, so mid-session expiry
is still caught by the global handler. Lighthouse (dev): Best Practices 96->100.