Verify runner prompt delivery and lifecycle regressions

Changes: Record verification evidence and replace the blocked S00-012 handoff with independent QA review instructions. Retain the existing stdin implementation and regressions from prior checkpoints; no new source changes.
Validation: Reproduced the legacy partial stdin timeout on Python 3.9.6 and reaped the child. All 28 automation tests passed, including exact 140024-byte UTF-8/EOF and timeout/submit descendant cleanup. make check passed all 72 tests; git diff --check passed. No live model, application readiness or Windows cleanup check is claimed.
