The two future-cancel cases — (future-cancel (future 1)) and the
future-cancelled? variant — depend on whether future-cancel catches a
trivial future in-flight, which is pure thread-scheduling luck. They were
allowlisted but still counted toward `pass` whenever the race resolved
favorably, so the floor (2728) silently assumed both passed. On a fast dev
machine they always pass; on CI's loaded shared runner one races to a
divergence, dropping pass to 2727 and failing the gate.
Skip them like the undelivered-promise case (neither pass nor fail) so the
race can't perturb the count. Floor drops to the deterministic 2726.
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