Fetch checklist by ID

Returns a single checklist along with its name, checkable_type/checkable_id (the record the checklist is attached to), allow_edit for the authenticated user, and progress counts (complete_count and count).

Visibility is determined automatically based on the authenticated user's role and the checklist's view flags — see the Checklists tag overview for details.

Required permission: assigned_event_read (when the authenticated user is assigned to the checklist's event) or unassigned_event_read (otherwise). User-checklists (personal task lists) are only visible to their owner.