* fix(#4058): raise MAX_ACK_TRAILERS from 64 to 128
64 had no principled derivation (no git trailer limit, no CI resource
bound) and a wide-touching maintenance PR can legitimately accumulate
more than 64 distinct emitted-drift acknowledgments, tripping the cap
and failing Required tests even though nothing is actually wrong.
The cap's underlying purpose is unchanged: parseAckTrailers() still
throws rather than truncates on overflow, and still forces pruning of
stale acknowledgments at some ceiling. Only the ceiling moves.
* chore(#4058): backfill changeset PR number (4059)
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Co-authored-by: sim <sim@local>
686c05a740