Avoid cloning ignored analytics notifications (#36020)

## What changed

- Pass server notifications to analytics tracking by reference.
- Clone only the notification variants that are recorded as analytics facts.

## Testing

- Add unit coverage that verifies a turn diff notification is enqueued and a command output delta notification is ignored.

GitOrigin-RevId: 2fa0711dbdcca33dce82c3ef78ee53a3f5a65bd9

codex-rs/app-server/src/outgoing_message.rs

@@ -161,7 +161,7 @@ impl ThreadScopedOutgoingMessageSender {
     pub(crate) async fn send_server_notification(&self, notification: ServerNotification) {
         self.outgoing
             .analytics_events_client
-            .track_notification(notification.clone());
+            .track_notification(&notification);
         if self.connection_ids.is_empty() {
             return;
         }