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

pi-mono.code-workspace

@@ -3,6 +3,9 @@
 		{
 			"name": "pi-mono",
 			"path": "."
+		},
+		{
+			"path": "../../moms"
 		}
 	],
 	"settings": {}