One extension's processes, with their own restart budget.

The budget is the point. asobi_sup is one_for_one with intensity 10 in 60 over eighteen children including the matchmaker, presence and every match and world supervisor. Without a per-extension boundary one crash-looping extension exhausts that shared budget and takes all of it down with no attribution.

sup/0 is read here, at init/1, rather than cached at resolve time, so a code upgrade that changes an extension's children takes effect on the next restart.