Each resolves to <root>/mailu/<id> — the maildir at
/var/lib/mailu/data-mail, certs at data-certs, and so on. Landing this
is a window, not an edit: seventeen renames on the node (the nested
data/ tree flattens to the ids), then the full stack recreated, because
a changed volume path does not recreate a container by itself (hq 126).
Ids are untouched on purpose — a renamed id orphans its held record,
and the mail spool is the wrong place to learn what a removal step does
with one.