With a PGLite config, buildGbrainEnv returned the caller env unchanged, so
a project's .env DATABASE_URL (autoloaded by Bun) reached gbrain: a false
broken-db at best, gbrain talking to the app's own Postgres at worst.
Inherited DATABASE_URL and GBRAIN_DATABASE_URL are now blanked for PGLite
configs (GSTACK_RESPECT_ENV_DATABASE_URL=1 still keeps them), and every
gbrain child runs from gbrain's config dir instead of the user's project,
so it cannot reload the project's .env / .env.local.
The old test that pinned pass-through for an engine:pglite config is
migrated: pass-through now applies only to configs that name neither a
database_url nor PGLite.
Co-authored-by: maxpetrusenkoagent <max.petrusenko.agent@gmail.com>
