mom: add events system for scheduled wake-ups

- Three event types: immediate, one-shot, periodic (cron)
- Events are JSON files in workspace/events/
- EventsWatcher with fs.watch, 100ms debounce
- Queue integration via SlackBot.enqueueEvent() (max 5)
- Fix setTyping race condition causing duplicate messages
- System prompt documents events for mom
- Design doc in docs/events.md
- Add croner dependency for cron scheduling

packages/mom/package.json

@@ -28,6 +28,7 @@
 		"@slack/socket-mode": "^2.0.0",
 		"@slack/web-api": "^7.0.0",
 		"chalk": "^5.6.2",
+		"croner": "^9.1.0",
 		"diff": "^8.0.2"
 	},
 	"devDependencies": {