ctrlrun.Event — class, defined at src/ctrlrun/receipt.py:154
event_id is assigned by the StateStore on append, not by the caller.
action_id is None for the three DELEGATION_* types (SPEC-v0.3 §7): they are about an
authority record, created and revoked outside any action’s life, and they name the
delegation in data.delegation_id. Inventing a synthetic action_id would put a value in
a field every reader takes to name a real proposal.