Notifications were too intrusive: install-success and export sat on
IMPORTANT_HIGH channels and produced heads-up alerts for every app,
while genuine download failures were buried in the IMPORTANCE_MIN
downloads channel where they were easily missed.
Restructure the channels around user intent:
- Download progress -> MIN, silent, no badge
- Installed apps -> LOW, silent (was HIGH)
- Updates available -> DEFAULT, silent
- App export -> LOW, silent (was HIGH)
- Errors & alerts -> HIGH (new, the only heads-up channel)
Failed downloads, installer-status errors and the unarchive auth prompt
now route to the high-importance alerts channel so they aren't lost,
while successful installs/exports stay quiet.
Android ignores importance edits on an already-created channel, so the
install/export channels get new IDs and the retired IDs (including the
folded-in account channel) are deleted on next launch.
012f4dcc26