The :memory: overrides in phpunit.xml had been commented out since 2024,
so RefreshDatabase ran migrate:fresh against the real .env database and
wiped it on every local test run. Enable the overrides, let the special
:memory: identifier bypass database_path() resolution and the boot-time
touch(), and add a TestCase guard that aborts the suite unless it is
pointed at in-memory sqlite.
ItemExportTest only ever passed by reading the populated dev database;
seed the root dashboard item it depends on so it passes on a fresh DB.