rules: a carried remake record taken from the coordinator its snapshot names

Review finding 7, second part: a record carried into a new epoch whole
(proposal and decision in one change) was taken from any member, for
any remake ID. A member could write a forged record, decision included,
for a fresh ID in a single change.

The snapshot's epoch metadata now names the remake's coordinator, as
the quorum built it. The carried-record exception holds only in a
later epoch, only for the remake that made it, and only from the
coordinator its snapshot names, where there is no record yet. Wire
version 43: the snapshot, and so the epoch ID, changes.

The review suggested carrying the record inside the snapshot instead.
The snapshot can't hold the decision, which names the snapshot's own
hash. So the snapshot vouches for who may carry the record instead.

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