chat-hook: consistently pull backlog subs
chat-hook: consistently pull backlog subs

We weren't accounting for backlog subscriptions with non-zero message
indexes in their wires. Now, we look through all of our outgoing
subscriptions to identify relevant backlog subscriptions, and leave all
of those.

The more proper fix here is to not include message indexes in the wire
in the first place, since we don't ever reuse that anywhere. But that's
a more invasive change, so we just leave a TODO for it instead.

ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,ngzax/urbit,jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit