add: cron automation placeholder

automations/cron/README.md

@@ -0,0 +1,19 @@
+# Cron Jobs
+
+Scheduled tasks that trigger agent workflows or infrastructure actions.
+
+## Format
+
+Each job is a bash script + a corresponding prompt file (if it calls Bedrock).
+
+```
+cron/
+├── scribe-daily-journal.sh
+├── inbox-triage.sh
+└── nightwatch-shutdown.sh
+```
+
+## Schedule
+
+Managed via system crontab on racknerd3.
+