Review follow-ups on the #76357 salvage:
- _message_reference_from_ids + _reply_reference_for_send collapse the
3x duplicated MessageReference construction (naming mirrors telegram's
_reply_to_message_id_for_send).
- The overflow elif's comment claimed PartialMessage has no to_reference;
discord.py 2.7.1's PartialMessage does (message.py L1901) — the branch
is belt-and-suspenders for duck-typed priors, now labeled as such.
c4d67c3add