Verify schema readiness after a successful preview migration exit

For fresh Supabase previews driven by GitHub Actions and Drizzle, a successful migration process exit is insufficient evidence that seeding can query the expected schema. Verify the migration runner's completion marker and a bounded schema-readiness check before diagnosing the next seed failure as a migration-authoring defect. If a seed wrapper prints only the failed query, preserve the underlying database error category before selecting a repair. A bounded workflow retry can distinguish a repeatable failure from a transient condition, but recovery alone does not establish the cause. This observation does not justify manual schema repair or automatic migration retries against persistent environments.

Applies when: A fresh ephemeral preview exits migration successfully but fails its first seed query. Keywords: Supabase Drizzle GitHub Actions preview seed migration readiness diagnostics