Every other QUIC test ends in std::_Exit(0), so nothing in the suite ever
ran a ~ClientQUIC. This adds 25 build-up/tear-down cycles with reader
threads parked inside RecieveSync -- the shape a reconnect loop has --
which aborts on ~10/20 runs against the current implementation.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
