apply_xtc: with probability xtcProbability, remove every token whose
probability exceeds the minimum above-threshold probability — i.e. drop
the top choices, keeping the least likely token that still clears the
threshold (plus everything below it). Special tokens are never removed.
key seeds the per-step uniform draw (the reference uses the global RNG).
apply_xtc: with probability xtcProbability, remove every token whose probability exceeds the minimum above-threshold probability — i.e. drop the top choices, keeping the least likely token that still clears the threshold (plus everything below it). Special tokens are never removed.
keyseeds the per-step uniform draw (the reference uses the global RNG).