SetRingtoneTool
Sets the default sound for a given type (ringtone / notification / alarm) via RingtoneManager.setActualDefaultRingtoneUri. Pass uri = "silent" to clear it.
Requires the special WRITE_SETTINGS access (Settings.System.canWrite); without it the tool returns an error pointing the user to system settings. Non-silent URIs must use the content:// scheme — file:// and other schemes are rejected.
Output keys: success, type, uri, is_silent.