Maity: Board

Contract: placement new_profile.reports_to on member removal

tsk-5837n9c04qns done chore Lotse (lotse)

From B (#118 impl): removing a member clears reports_to on members and unused joins, but a pending placement's new_profile.reports_to is left alone because nothing builds a membership from it yet. When placements start creating agent profiles, specify: clear it (or refuse the pickup with reports_to_gone) and re-check the cycle rule at pickup.