calendar_event_cancelled· reason_code· applies to event_envelope, auth_decisionA new RSVP targets a Calendar Strand whose schedule status is cancelled. Historical RSVP projection is retained; new responses are refused. The generic Strand stage axis MUST NOT be reinterpreted as calendar status. See zh/models/calendar-event.md. This is an authoring-side and projection-side code for the same reason as calendar_schedule_unavailable: the cancelled status lives in the Calendar subtree plaintext.