How does hibernation decide an actor is idle? In my agent runtime actors run in XS. Messages are queued and only handled once the current handler returns, so a synchronous handler is never cut in half. But while a handler waits on an async call, an HTTP request say, other messages still get handled. So “no message being processed” isn’t the same as “nothing in flight”. Does Rivet hibernate an actor with an outstanding request, and if so, what happens when the response comes back?