#982 Unit tests that depend on production database state fail on an empty database

EARS: The superproject and engine unit suites shall pass against an empty database built from the migrations, with no rows they did not create themselves. Found by the #918 tests job (empty PostgreSQL 16 + pgvector, migrations merged in id order, auth_rbac and breaker tables created, max_connections 260): - tests/unit/test_tenant_rate_limiter.py test_refill_token, test_refill_capped_at_max_tokens, test_get_tenant_stats (both the superproject copy and the identical engine copy): SELECT ... WHERE tenant_id='test' returns no row. check_quota auto-provisions the row but the test connection is closed without commit, so the row only exists on a database that already had it. - Remaining failures after config and keys are provided are listed on #918 with the measured run.