Per operator: under the SiteLink IP plan there should never be
GUID/MAC/IP conflicts. Reframed the merge checks accordingly - they
are tripwires for plan drift (un-renumbered site) or stale inventory
(same pod recorded in two site files), not expected events. The merge
now exits 3 when any warning fired (master still written) so event-day
scripts can gate on a clean merge; 0 = clean, 1 = usage, 2 = hard
error. Verified: same-file-twice merge exits 3, clean merge exits 0.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>