feat(events): add Close() method to ChannelEmitter

Allows consumers to signal the drain goroutine to stop by closing
the underlying channel. Used by CLI dispatch watch cleanup.

Co-Authored-By: Charon <charon@lethean.io>

events.go

@@ -78,6 +78,11 @@ func (e *ChannelEmitter) Events() <-chan Event {
 	return e.ch
 }
 
+// Close closes the underlying channel, signalling consumers to stop reading.
+func (e *ChannelEmitter) Close() {
+	close(e.ch)
+}
+
 // MultiEmitter fans out events to multiple emitters. Emission continues even
 // if one emitter fails — errors are collected but not returned.
 type MultiEmitter struct {