fault.sx run-safe: a node op may return (artdag/fail reason); failure is confined
to that node + downstream dependents while independent branches compute, and failed
results are never cached, so retry after a fix recomputes only the failed closure
and hits the good nodes. fault 14/14, total 158/158.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
