Scheduled-job manager for Merlion Agent.
Jobs are stored in ~/.merlion/cron.yaml as a list of (name, schedule, prompt) triples where schedule is a 5-field POSIX cron expression
(with an optional 6th seconds field — the cron crate's default). When
merlion cron daemon runs, each job fires at its scheduled time and
the resulting agent response is logged (or delivered through a
gateway, if configured).