A Retire that reached an actor still dialling was queued behind the
connection and, if that dial then failed, never applied: nothing in the
registry pointed at the actor any more, so its thread lived on. Nothing
has gone out on a dial in progress, so retiring one closes it on the
spot.
A retired actor reads only from its tick, and one socket buffer a tick
is 10 KiB a second: a real share listing would outlast the grace. Every
actor now drains up to 64 buffers a tick.