blueprint_mc_family joins its sweep/walkforward siblings on the
51096a3 machinery: catch_member_panic around the bare member run in
the monte_carlo draw closure, per-seed capture, lowest-seed
resolution after the join (seed-input order, thread-order-independent,
C1), exit via the shared aura: warning: + exit 3 path. Ordering is
load-bearing and documented at the site: the captured fault resolves
BEFORE the vacuous-mc guard, so metrics-identical placeholder reports
from faulted draws cannot masquerade as a vacuous run. All three
containment e2es green; clippy clean. refs #278
claude
a20b6f6003