R2.x live-ref cleanup. If this update is destructed directly
while still hosted (the misuse path — the chokepoint
unhostUpdate clears _host before it destructs, so the
host-driven path sees a null ref and no-ops here), detach the
stale reference from the host's collection. No re-destruct: we
are already mid-destruct. The host-destruct path clears each
update's _host first, so this also no-ops there.
R2.x live-ref cleanup. If this update is destructed directly while still hosted (the misuse path — the chokepoint
unhostUpdateclears_hostbefore it destructs, so the host-driven path sees a null ref and no-ops here), detach the stale reference from the host's collection. No re-destruct: we are already mid-destruct. The host-destruct path clears each update's_hostfirst, so this also no-ops there.