Returns one notification from the bearer Person's inbox. Person-scoped (rejects X-Wingspan-Account with 400 AccountScopeNotApplicable; cross-Person access returns 404). The inbox is single-owner and view/dismiss transitions are monotonic and idempotent (Active to Viewed to Dismissed); concurrent writers cannot produce a lost-update anomaly, so ETag/If-Match is intentionally omitted and no version field is exposed.