Preview what removing a member would break

Previews what removing this member would break, before anything is changed. Lists every connection they own (all are deleted on removal), each with references (exact counts of the toolboxes and other members' synthetic tools using it, plus at most five names) and up to ten replacement_candidates (same connector, active, not the leaver's, usable by you; owner named) beside an exact replacement_candidate_count. credentials counts the API tokens and AI client logins that removal revokes. Separately, delegated_entries lists entries on other members' toolboxes whose pin currently rides on this member's own use grant, not their ownership. This is non-blocking, and member removal never refuses over it, but once the member is gone those entries go unmet until somebody with their own use on the connection re-pins them; nothing does that automatically. connectors lists every custom connector the member owns, each with a short shared_with summary and a connection_count. Read-only: call it before DELETE /member/{userId} to collect the hand-over and replacement decisions that call takes. Requires member:manage.