Mounts and ship interaction

Mounted run/swim stamina uses lerp(1,0.5,ridingSkill)*configuredDrain*dt; exhausted running becomes walking. Any nonzero owner-authoritative stamina use resets the one-second regeneration delay. Regeneration after its delay uses the hungry/normal base rate*(2-current/max)*dt, capped at maximum, while not attacking or swimming. An exhausted swimming mount takes ceil(maxHealth/20) raw drowning damage after each strict one-second check. Riding skill is raised on running interval checks. Ship steering requires a nearby unencumbered player aboard and owner-granted control. Ship constructors spawn their configured ship after elapsed network minutes exceeds construction time.