mapper

The mapper of a state's JSON: WowJson's, which reads a val with no setter into its field as 9.x's JSON did, with the settings a state's round trip needs besides. A getter of its own (val items: List<Item> get() = lines) is not read: a getter that computes an immutable collection of an event or a state reads back, and a state that keeps a collection behind such a getter does not, so its snapshot is refused and its log replayed.