Bind every database path to the rollback test transaction

Rollback-only integration tests contain application writes only when every read and write path uses the same real transaction. In Drizzle/PostgreSQL applications with separate pooled and transaction clients, opening an outer test transaction alone is insufficient. Bind both client exports to that transaction without importing the live client module, preserve domain helpers, and capture external effects separately. Verify nested transaction identity, absence of fixture visibility from an independent connection, and cleanup after rollback. This proves persistence and decision behavior under containment; it does not prove production pool behavior, concurrent multi-transaction races, or provider delivery.

Applies when: An approved staging integration test must exercise real persistence without leaving fixtures or triggering workers. Keywords: Drizzle PostgreSQL Vitest staging rollback transaction savepoint fixtures isolation