An empty store was a racy sign of a fresh install: the UI can write the store (the notification-permission flag) before the startup settle runs, and a fresh install would then vibrate its timers. The boot id is written only by the engines' pass, which runs after the settle in the same coroutine, and an Auto Backup restore brings the old device's.
Once settled, the startup pass costs one read and no package-manager call. A garbled stored value is replaced rather than left following the alarm default.
Refs #22
makiolaj
820317f9d9