Remove a trainee from the coach account. This ends the active escort, cancels their upcoming meetings, unlinks their training plan and nutrition menu and deletes their gamification profile.

The trainee is archived rather than erased: their account, history and measurements are kept, they stop counting against your trainee limit, and they disappear from GET /trainees and from GET /trainees/{traineeId}, which answers 403 for them afterwards. List archived trainees with GET /trainees?status=archived and bring one back with POST /trainees/{traineeId}/restore.