Updates name, birth date, visibility, favorite status, or thumbnail on multiple people in one transactional call. Each item carries the target person id and the per-person change — different fields can be changed on different people in the same request. Atomic: a duplicate id, an unknown or inaccessible id, or any per-item failure rejects the whole batch and writes nothing.

Items apply in request order, and each rename is checked against the names left by earlier items: swapping two people's names, or giving two people the same name, returns 409. Renaming to another record's name in the same library, including hidden people, also returns 409. Names ignore case and surrounding whitespace; retrying the same collision does not resolve it.

update_person edits a single person.