Issue 108: the artifact store has never collected anything. Fifty-three
repositories on the machine that serves everything else, and the only outcome
of leaving it is a full disk reported as somebody else's failure.
The mesh decides what may go — from its own build records, so it never names
a digest it did not put there — and the store reclaims the bytes in a nightly
window with its server held still. Deletion on the one door takes nothing a
push did not already have.
Designs 18 and 20 amended; issue 108 resolved.
Also issue 202, found running the controller's suite: a module whose required
setting nobody set is left out of the machine in silence, and dnsmasq became
that module this morning.