Versioning

Every save and activation is versioned. The engineer guide walks through it: Versions, history and rollback.

Status	Meaning
Draft	Editable head; never served cases, or a fork of the active version
Active	Live; new cases run on it
Superseded	Replaced by a newer activation
Disabled	Deactivated explicitly

Saving an active version forks a new draft; the live version keeps serving cases.
Activating a draft makes it live and supersedes the previous active version.
History in the builder lists every lifecycle change with actor and time.
Older versions open read-only (?version=N). There is no rollback button: edit the head to match and activate.