chore(archive): preserve KNELServerBuild remainder + layout notes [#474]

Archive the non-ported remainder of the legacy KNELServerBuild repo
under archive/KNELServerBuild/ with its original structure intact,
completing the legacy repo merge for everything except the live
LibreNMS patterns (ported in the previous commit).

Exclusions:
- .git history (superseded; legacy repo remains at its original path)
- ported files (Agents/librenms, Modules/OAM/oam-librenms.sh,
  ConfigFiles/SNMP/snmp-sudo.conf)
- vendored KNELShellFramework tree (byte-identical duplicate of the
  copy already vendored at vendor/ in this repo)
- SSH authorized-keys files (live access-control material; carrying
  them in an archive invites drift — key policy lives elsewhere)

The whole tree is skip-listed in tests/shellcheck.sh (archived legacy
code, not maintained — same standing as vendor/); check-rules.sh
already prunes archive/. Rule 9 (conflict markers) now also excludes
archive/ staged files: preserved-verbatim legacy scripts contain
decorative "====" banners that false-positive as conflict markers
(same archive exclusion precedent as rule 11).

AGENTS.md: note archive/KNELServerBuild and oam/librenms-agent in the
Repository Layout, and fix the stale KNELIAC path to
/home/reachableceo/projects/KNEL/KNELIAC.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

archive/KNELServerBuild/Project-Includes/PreflightCheck.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+function PreflightCheck()
+{
+
+export curr_user="$USER"
+export user_check
+
+user_check="$(echo "$curr_user" | grep -c root)"
+
+
+if [ $user_check -ne 1 ]; then
+    print_error "Must run as root."
+    error_out
+fi
+
+echo "All checks passed...."
+
+}