README step 4 used an inline apply_schema over the app DATABASE_URL, which fails
under the privilege model (least-privilege app role cannot run DDL). Replace it
with 'codex migrate' and document MIGRATION_DATABASE_URL (owner/superuser) in the
README env table and .env.example, so the privileged migrate path is the
standard for future schema upgrades.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>