Mirrors the postgres bed for minio: a provider (runtime carries mc) + a consumer
requiring s3-bucket, proving the consumer reaches its bucket with the access key and
secret the mesh delivered. It surfaced a real limit: the mesh derives `as` =
mesh_<node>_<module> (22 chars), and an S3 access key is capped at 20, so minio refuses
the service account. The test is correct and skipped pending 04-ISSUES/010, not worked
around.
Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF