resolveAndConnect discarded the actual error from connectUpstream
(ECONNREFUSED, ETIMEDOUT, an ssh2 auth failure, ...) and replaced it with
the generic reason string 'upstream-unreachable', so the audit log gave no
way to tell a network-layer failure from an auth failure -- which is why
"Could not reach 192.168.1.206" for the emby host couldn't be root-caused
without live host-shell access. Now the real error message is captured and
surfaced as failDetail, shown as a tooltip on the audit table's fail badge.