Inbound message handling gets an explicit disposable queueing handle

What

• The peer-messaging and bridge:repl inbound-message handlers now hold onto a queueing object returned alongside the message content. It's declared with using (a pattern that runs cleanup automatically), and the handler calls .queued() once the message is actually enqueued; if the handler returns early without enqueueing, the cleanup logic fires instead.
• The session.receive hook dispatch path now always returns a queueing field too: a no-op placeholder when no hook is registered, or a real one tied to an arrival-tracking mechanism when a hook consumes or holds onto the message.

Why

This ensures that whenever a message is received, there's a reliable, explicit way to know whether it was actually queued or dropped, so cleanup happens correctly in both cases instead of relying on implicit behavior.