pub fn apply(state: &mut RunState, event: &JournalEvent)Expand description
Apply a single event to state, in place.
Idempotent: an event whose seq is at or below state.applied_seq is
skipped (the high-water mark), and every mutation targets a keyed set/map, so
re-applying a seen event leaves the state byte-identical. This is what makes
append-then-apply crash-safe — replaying after a crash is a clean
no-op-or-apply.
Terminal-safe: once the run is RunStatus::Completed or
RunStatus::Abandoned, further events are ignored (the watermark still
advances so a later legitimate replay is consistent), so a corrupt log cannot
mutate a run past its terminal fact.