Create a scheduled task that runs on a cron schedule. The task will execute the given prompt at the specified intervals.

Cron expression format: "M H DoM Mon DoW" (5 fields, in local time)
Examples:
- "*/5 * * * *" = every 5 minutes
- "0 9 * * *" = daily at 9am
- "0 9 * * 1" = every Monday at 9am
- "30 14 28 2 *" = Feb 28 at 2:30pm

Set recurring=false for one-shot tasks. Set durable=true to persist across session restarts.