Assigns a postgres provider (its runtime carries psql) and a module that requires
postgres-database; the mesh mints one password, postgres's provisioner creates a role
and database under the mesh's login with it, and the consumer connects to its database
with the delivered credential (a password-checked connection) — select 1. Nothing placed
by the test. The postgres half of the per-backend provider proof (ADR 0052/0053).
Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF
