* feat(cron): render scheduled reminders in TUI and expose fired events
- add CronMessageComponent for distinct cron transcript entries in TUI
- emit cron.fired events from agent-core and expose via node-sdk
- report cron fire times with local ISO timestamps including timezone offsets
- render cron_job and cron_missed origins during session replay instead of skipping
- handle warning events in CLI and session event handler
* docs(cron): clarify that users must ask the model to manage cron tasks
- cron-create.md: instruct model to proactively tell users how to cancel/modify reminders
- cron-list.md: add guideline that users cannot directly manage cron tasks\n- cron-delete.md: emphasize users must ask model to cancel reminders
