CREATE DATABASE IF NOT EXISTS reuses the prior run's data, so the test DB
would itself accumulate users run-over-run (the same flaky list_shares
fan-out the dev DB suffered). Truncate every table (except the drizzle
migration ledger) at globalSetup start, FK-safe, so each run is a clean
deterministic slate. Verified: familysync_test users 186 -> 93 across a run
(reset, not doubled); dev familysync untouched at 3.