maven: fix test mocks for CalendarEvents interface (verification)

- Add CalendarEvents method to recordingAPI in auth_test.go
- Add CalendarEvents method to fakeCore in handlers_test.go

Co-Authored-By: opencode <opencode@anthropic.com>

cmd/mavenclient/main.go

@@ -21,8 +21,8 @@
 // delivery end-to-end. The reference for "the most-recently-active client
 // plays it": run one, fire a tick, see the file appear.
 //
-//	 mavenclient -listen -out-prefix /tmp/maven-nudge-
-//	 # then trigger a tick; /tmp/maven-nudge-1.wav, -2.wav ... appear
+//	mavenclient -listen -out-prefix /tmp/maven-nudge-
+//	# then trigger a tick; /tmp/maven-nudge-1.wav, -2.wav ... appear
 package main
 
 import (
@@ -160,4 +160,4 @@ func jsonUnmarshal(b []byte, v any) error { return json.Unmarshal(b, v) }
 var _ = strconv.Atoi
 var _ io.Reader = (io.Reader)(nil)
 var _ = net.IPv4
-var _ = time.Second
+var _ = time.Second