feat(oam): port LibreNMS agent tooling from KNELServerBuild [#474]

Port the live LibreNMS monitoring patterns from the legacy
KNELServerBuild repo into oam/librenms-agent/, joining the existing
OAM tooling (oxidized, unpoller, smokeping, netdisco):

- agent/ — upstream check_mk agent + snmp-extend scripts (dmi, dpkg,
  mysql, ntp-client, ntp-server, os-updates, postfix, raspberry, smart,
  ss, ups-nut), copied verbatim (md5-verified), never to be edited here
- setup.sh — deploy module ported from ProjectCode/Modules/OAM/
  oam-librenms.sh; only the legacy framework bootstrap was replaced
  with plain bash (path constants + print_info -> echo)
- snmp-sudo.conf — Debian snmpd sudo rule the extends require
  (Debian-snmp NOPASSWD /bin/cat); carried as a file only, sudoers
  install is a policy decision per AGENTS.md

Lint gates: extend the existing upstream-skip mechanism for the
verbatim agent scripts (tests/shellcheck.sh + check-rules.sh prune,
same precedent as archive/provisioning/Agents/librenms), and fix the
stale skip path there (provisioning/ moved to archive/provisioning in
6244c1c; the bash extends have been failing the whole-repo shellcheck
gate since).

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

tests/shellcheck.sh

@@ -22,8 +22,10 @@ mapfile -t FILES < <(
     for f in "$@"; do
       f_abs="$(cd "$(dirname "$f")" && pwd)/$(basename "$f")"
       case "$f_abs" in
-        "$ROOT"/vendor/*) ;;                      # skip vendored
-        "$ROOT"/provisioning/Agents/librenms/*) ;; # upstream librenms-agent scripts
+        "$ROOT"/vendor/*) ;;                              # skip vendored
+        "$ROOT"/archive/provisioning/Agents/librenms/*) ;; # upstream librenms-agent scripts
+        "$ROOT"/oam/librenms-agent/agent/*) ;;             # upstream librenms-agent scripts (verbatim port [#474])
+        "$ROOT"/archive/KNELServerBuild/*) ;;              # archived legacy code, not maintained [#474]
         *) case "$f_abs" in *.sh) echo "$f_abs";; esac ;;
       esac
     done
@@ -31,8 +33,10 @@ mapfile -t FILES < <(
     # Default: every .sh under the repo, minus vendor/
     while IFS= read -r f_abs; do
       case "$f_abs" in
-        "$ROOT"/vendor/*) ;;                      # skip vendored
-        "$ROOT"/provisioning/Agents/librenms/*) ;; # upstream librenms-agent scripts
+        "$ROOT"/vendor/*) ;;                              # skip vendored
+        "$ROOT"/archive/provisioning/Agents/librenms/*) ;; # upstream librenms-agent scripts
+        "$ROOT"/oam/librenms-agent/agent/*) ;;             # upstream librenms-agent scripts (verbatim port [#474])
+        "$ROOT"/archive/KNELServerBuild/*) ;;              # archived legacy code, not maintained [#474]
         *) echo "$f_abs" ;;
       esac
     done < <(find "$ROOT" -type f -name '*.sh' \