A's emergency flow is inherit -> commit -> put the dead corner down -> roll, and
it goes through session.commit(rig) by design (the public-moves discipline).
That door could not seed the sail's clock, so getting it right needed a SECOND
call after commit — a step a caller can forget, on the one night where
forgetting it understates every load ~4x and reads as "triage is easy" rather
than as a bug. opts forward straight to attach; omitted, the ordinary night is
byte-for-byte unchanged (clock at 0), pinned both ways.
Selftest 535/0/0 (522 baseline + 13).