db: TestSetSessionUserModesIsAtomic installs a trigger that rejects the
is_oper UPDATE after the is_wallops UPDATE has run, proving the '+w-o'
partial-failure the old independent-UPDATE loop exhibited is gone.
ircserver: TestDisconnectDoesNotBlockOnUnresponsiveVictim drives
Disconnect against a net.Pipe victim that never reads and requires the
call to return promptly; verified to fail against the synchronous
implementation. Its counterpart asserts the notification is still
delivered and the socket still closed.
