Why: Home and sibling isolation tests could pass after a Bubblewrap startup failure, hiding an untested security boundary.
Evidence: Isolated fake-Bubblewrap replay changed both target tests from PASS to FAIL; SELF receipt /tmp/dependency-task1-fake-green-20261014-01a1345f.json. Native positive replay remains NOT_RUN.
Impact: Test assertions only; production execution behavior is unchanged.
Refs: Backend PR #196; Documents design 1790cf8