Actus 1.1.0

Added

• Server::run_listener / Server::run_with_shutdown_listener — serve on a
  listener the caller already bound or inherited. This is the socket
  activation entry point (systemd LISTEN_FDS, launchd): the supervisor
  owns the socket, so connections arriving during a process restart queue in
  the kernel's accept backlog instead of being refused, and the next process
  serves them. Also the race-free shape for tests and embedding (bind
  127.0.0.1:0, keep the listener, pass it in). run_with_shutdown_on is
  now a thin bind-then-delegate over the listener form; behavior of every
  existing run* method is unchanged.