declareSpectatorsClosed

Publishes the spectators-closed signal on the host's presence slot.

Call this when spectators are disabled (gameHost allowSpectators = false) or when maxSpectators has been reached. Appends SPECTATORS_CLOSED_SUFFIX to whatever value the host's slot currently holds, so the signal coexists with admissionClosed.

The signal is monotone — once published it is never retracted.