PASS pair_commit: incomplete transfers never modify published bytes
PASS mapping: 15+5*12+13, every key 0..87 appears once
PASS mode: polarity write and readback failures prevent valid samples
PASS isolated_failure: healthy board advances; stale note released once
PASS recovery: held key cannot retrigger before an observed release
PASS ownership: fault release preserves touch and automatic-player owners
PASS time: unsigned wrap and delayed-poll recovery obey stale threshold
PASS fault_scope: all 88 single-key failures release only their key
PASS retry_and_mask: bounded retries, missing-at-boot recovery, unused bits ignored
ALL 9 CHECK GROUPS PASSED (host mock bus, not physical hardware)
