PCT for the first K steps, then uniform random walk.
Coyote uses this hybrid as a probabilistically-fair PCT. Pure PCT can
livelock on programs with spin loops because a high-priority process
spinning on a low-priority process starves it. After step K we fall
back to random scheduling, which is probabilistically fair.
Options
Inherits all of Lockstep.Strategy.PCT's options, plus:
:fair_switch— step at which to flip to random; defaults todiv(max_steps, 2).