The idea behind the previous implementation worked, but it was a tad bit
confusing. This commit refactors the activation logic by simply removing
it entirely. The "activation" part of the logic is now derived from the
wave number (if 0, it means we haven't _really_ started yet), instead of
relying on the spawn thread to toggle the flag on and off. This kind of
dependency inversion (spawn thread -> listener, listener -> "phase") is
a pretty decent (albeit super tiny) step towards cleaning up the whole
session system, so I call that a victory in and of itself!
Andreas Troelsen
457bf2ffff