Tasks 4.3, 5.2 and 5.4 are done as of 2026-09-28 02:25: every machine reports on
the new bus, the seat is held by the module that provides it, the old broker is
unassigned and forgotten, and every credential was minted afresh at the end.
5.2 records what it took, in the order it was found and each fixed on the trunk
before the next step, and how the bootstrap loop was broken once, by hand.