Move an already-approved physician between labeler and reviewer.

Deliberately not part of the approval endpoint. Approval decides whether somebody works here at all and carries a first tier as one of its outputs; this is the smaller, later thing, and keeping them separate means a promotion cannot accidentally re-run the side effects of an approval (credentials minted, welcome mail, community post).

A note is required for the same reason a rejection requires one: in six months the only person who can explain a role change is whoever wrote it down at the time.