Journaled grain state notifications

Override OnStateChanged to react after the confirmed version can have increased:

protected override void OnStateChanged()
{
    // Inspect State and Version.
}

It can run after loading a newer state, confirming a local event, or receiving a protocol notification. It isn’t an exactly-once integration-event callback. Don’t perform an external side effect here unless the application adds its own idempotency or outbox protocol.

Override OnTentativeStateChanged to react when the tentative view changes:

protected override void OnTentativeStateChanged()
{
    // Inspect TentativeState and UnconfirmedEvents.
}

RaiseEvent triggers this callback. It can also run when confirmation or synchronization changes the tentative suffix.

Both callbacks execute under Orleans turn-based scheduling. They should be quick and must not assume that their observed state remains unchanged across a later await.