Move nightlight from niri spawn-at-startup to a systemd user service
with After=kanshi.service to ensure all outputs are configured before
wlsunset starts. Toggle now uses enable/disable --now for persistent
state across reboots.
Diagnostic script that verifies services, configs, packages and paths
against the expected moonarch system state. Reports pass/fail/warn with
colored output and summary. Deployed as moonarch-doctor (alias: moondoc).
