Store received messages with complete wire recipient lists

[markmnl]

Inbound storage truncated a message's recipients to the locally accepted ones, discarding co-recipients on other domains. That broke the participant record (hosts disagreed on a message's recipients), and worse, broke SPEC §10.3 participant validation: a reply from a co-recipient this host never recorded would be rejected as invalid. It also made faithful reconstruction of the message impossible, which SPEC §11 hash computation depends on.

storeMsgDetail now stores the complete wire to/add to lists in wire order. Recipients this host accepted are marked delivered as before; recipients it rejected keep the per-recipient code it responded; and recipients on other domains carry the new local sentinel response code -2 (not our delivery) so the sender's pending queries never treat them as this host's work. attachAddToRecipients and storeMsgHeaderOnly use the same sentinel (previously code 11).

Received messages additionally persist their exact wire header bytes in the new msg.wire_header column so any hash -- including future add-to batch variants -- can always be recomputed faithfully, immune to re-encode drift. Locally-authored messages leave it null.

Existing rows cannot be backfilled; the discarded recipients were lost at receive time. Upgrade path for existing databases:
alter table msg add column if not exists wire_header bytea;
(no other schema change; the sentinel uses the existing response_code column).