(and of course it fails...)

they were introduced as `queue` module queues, but actually the values
(and the annotations used at the other end of the router_starter call)
are multiprocessing.Queue (subclasses...)

mypy does not typecheck this call... a later PR introduces typeguard here
(which detects this)

this hasn't caused execution problems - the APIs of the two queue types are close enough
- but it is incorrect when trying to understand how pieces of monitoring
communicate with each other.

…there are multiple Queue types floating around with very similar interfaces

…otations in modern type syntax

…eguard-types