PrefsRecovery.assertStoreReadable reads the real on-disk store through
path_provider, and on the hosts where it is active (Linux and Windows)
that genuine file IO can never complete inside testWidgets' fake async
zone. Since 7f0cad33 wired the preflight into shared-preference init,
every widget test that initialises settings on the Linux CI runner hung
for its full ten-minute timeout, turning the unit-test job into a
six-hour cancellation. The hermetic prefs fixture swaps the backends for
in-memory fakes anyway, so it now disables the preflight and restores it
on teardown; the repair-flow suite keeps opting in explicitly.
Verified in an ubuntu-24.04 container on Flutter 3.44.0: the full suite
now completes in nine minutes with zero failures.
edde746