Let the held breath out — clear the grace.
The species breathable set (default ['air']; water-breaters ['water']).
Take and hold a breath — extend the breath-hold grace (free-diving).
Whether a voluntary/automatic breath-hold is currently active.
Whether this body respires at all (the respires opt-out).
The traverse hook (the Mobile.onTraversed shape) — fires reassess on every move.
The central event-driven re-resolve: engage/cancel the crisis drain.
Emission body of the drain engagement (delegated from RespirationDrain).
Game-time (seconds) of the last drain/recovery tick; 0 = unseeded.