In particular:
1. The root facet is considered inert even if it has outbound
assertions. This is because the only outbound assertion it can have is
a half-link to a peer actor, which shouldn't prevent the actor from
terminating normally if the user-level "root" facet stops.
2. On stop_facet_and_continue, parent-facet continuations execute
inline rather than at commit time. This is so that a user-level "root"
facet can *replace* itself. Remains to be properly exercised/tested.
Tony Garnock-Jones