The tripwire is aimed at Lane C's incoming hailAt(): the router swallowed C's
rain API silently once already, and decision 13 hangs the whole garden score off
hail, so the same omission would recreate the exact problem Sprint 5 exists to
fix. Also records that Sprint 4's headline finding was re-measured against a true
control and survived.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>