-- A machine's report says which container it left running because it said busy, and which it replaced
-- after it waited (novox/hq ADR 0335, issue 594).
--
-- A send that replaced the build agent killed the check it ran, and the queue started it again elsewhere.
-- A container may now declare `busy`; the node-engine asks it before replacing it, leaves it running while it
-- says busy, within 15 minutes, and says so in its report's `busy`: [{"id", "container", "state", "since",
-- "until", "said"}], state `waiting`, `replaced-when-idle` or `replaced-at-bound`. Kept with the machine's
-- last account, so a walk's first-machine gate waits while its module's container is listed waiting — across
-- a restart of the controller, which a merge into mesh-controller makes in the same walk that moves the build
-- agent. Empty from an engine that never waits.
alter table node_report add column busy jsonb not null default '[]';