Ask the other institution to review a match

Asks the other organization involved in this match to review its own side and record a determination. Face images are never shared between consortium members, so when a human needs a second opinion on a borderline match (a near-threshold similarity, a suspected sibling or twin) this moves the *question* rather than the applicant's photo: the peer looks at the record it already holds, and only their investigation status crosses the organization boundary. Idempotent for 24 hours — re-requesting while a request is still outstanding returns `already_pending` and does not re-notify the peer. The pending state is visible on the match as `peer_investigation.review_requested_at`.