Scheduled tasks (cron) for DeepSeek Harness

Key features

• dsh-cron owns schedule parsing, timezone calculation, durable occurrence identity, catch-up policy, and the task-center UI.
• five-field cronminute, hour, day-of-month, month, day-of-week
• deterministic occurrenceId, scheduledAt, and idempotencyKey
• dsh-automation owns the Run queue, canonical fresh Sessions, cross-worker concurrency, cancellation, explicit retries, event history, retention, and crash recovery.
• dsh-webhook is the equivalent event-driven Trigger adapter and optionally provides outbound settlement callbacks.