trello.onChecklistUpdated matches Trello’s updateChecklist action.
automations/watch-trello-checklist-updates.automation.ts
board as an ID, short link, or URL. Optional static account defaults to the project binding.
Returns a resource event with actionType: "updateChecklist", required checklist and board, plus actionId, occurredAt, optional card, old, memberCreator, and the complete provider event.