The three wedged-child scenarios busy-spin their worker for 1.5s while the
host waits for the start RPC; under a loaded 2-core CI runner (this branch
adds several parallel suites) the RPC lands after vi.waitFor default 1s,
failing the coverage lane three runs in a row at the same three sites. An
explicit 10s waitFor timeout (well inside each test own 15s budget) makes
the assertions load-tolerant without weakening them. Belongs upstream with
dsh-workflow-workerthread; carried here because it gates this PR.