onNotificationPermissionGranted

Called after the operator grants POST_NOTIFICATIONS from the keep-alive prompt.

A foreground service started while that permission was denied has its notification suppressed by the platform, and granting the permission afterwards does not retroactively post it -- the notification only appears once something calls startForeground again. Without this hook the operator allows notifications, is told nothing more, and still sees no notification, which looks exactly like the keep-alive service not running at all.

Defaults to a no-op for adapters with no server lifecycle to re-notify.