Op mentions in the follow up comments that he does a separate git checkout, one for each of the 5 Claude Code agents he runs. So each is independent and when PRs get submitted that's where the merging happens.
Yes. The 2 types of earthquake alerts each have a unique sound that was designed specifically for earthquake alerts. They are available in the supplemental data folder that's associated with the paper (you can also hear one of these by going into the android earthquake settings and clicking on the Demo feature).
Receiving alerts should be on by default as long as you're in one of the supported countries. You can verify by going to settings, safety and emergency, earthquake alerts.