Every non-Found outcome was collapsed into NO_CALENDARS, so a server
whose login flow named an unresolvable host told the user their account
holds no task lists. Both Failed and NotCalDav already carry the cause
discovery worked out; forward it and keep NO_CALENDARS for the outcomes
that really mean it.
This is what turned the overwrite.cli.url skew from confusing into
undiagnosable: the user retries, gets the same wrong answer, and leaves
another spent app password in their device list each time.