SetDndModeTool
Sets the Do Not Disturb interruption filter.
Calls android.app.NotificationManager.setInterruptionFilter. Requires DND policy access (isNotificationPolicyAccessGranted), a special access granted via Settings > Apps > Special access > Do Not Disturb access; without it the tool returns an error. Idempotent (setting the same mode twice has the same effect).
Output keys: success, mode.