If we left a subscription in the middle of peeking for a multi-fragmemnt $boon, and the %cork $ack came before the $boon page was delivered, we would create a space leak in the .pit by not removing the payload peek.

I reorder the code a bit here and also to move the logic for peeking for multifragment payloads into the flow layer.

Also, I (re)add the authentication for the %auth fragment in a %poke, that was somehow not pushed?(probably due to some merge conflicts)