CallHeader
The Wow-Call header: the root command a service's synchronous call acts for, a CallWire, as the base64url (unpadded) of its JSON. One header carries it all, so one rule guards it: the edge takes it from a service identity only, and refuses it from any other caller.
It is the framework's own header between its services, opaque to clients. This object is its framing; the JSON of a CallWire is Wow's one JSON configuration (WowJson), which the API does not depend on.