A host's node_exporter stops as soon as a shutdown begins and a normal
reboot takes about 3-5 minutes, so the 2-check failure_threshold cut a
ticket for planned reboots. Add monitor.host_failure_threshold, default 5,
for hosts with no metrics and ping-only hosts. Interface link-down alerts
keep the shorter threshold, and the dashboard still shows the host as down
straight away.
Closes#14
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>