The sound Google Clock and BlackyHawky's Clock use for timers is
timer_expire.ogg from AOSP DeskClock, bundled with those apps rather
than installed as a system ringtone, so RingtoneManager never lists it.
It is now bundled here too and listed first in every sound picker.
The choice is stored as clockula://tone/timer_expired and resolved to
the raw resource when played, so it survives a restore into another
build variant. The file is Apache-2.0, recorded in docs/PROVENANCE.md
with the licence text in licenses/.
Fixes#14