feat: exclusive pilot — spool flush and verify script

Replay spool on each monitor loop; sac_post_payload refactor;
pilot-verify-exclusive.sh and --check-sac hints for exclusive mode.

update_ssh_monitor.sh

@@ -426,8 +426,9 @@ print_config_variables_help() {
        TELEGRAM_BOT_TOKEN, TELEGRAM_CHAT_ID
        — или MAIL_SMTP_HOST, MAIL_FROM, MAIL_TO
 
-     Security Alert Center (рекомендуется dual на пилоте):
-       UseSAC=dual
+     Security Alert Center:
+       UseSAC=off | dual | exclusive | fallback
+       Пилот 2.1 (только SAC): UseSAC=exclusive
        SAC_URL=https://sac.kalinamall.ru
        SAC_API_KEY=<ключ из SAC sac-api.env / bootstrap>