fix(#4058): raise MAX_ACK_TRAILERS from 64 to 128 (#4059)

* 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)

---------

Co-authored-by: sim <sim@local>

.changeset/patient-elks-glide.md

@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 4059
+---
+**Raised the emitted-drift acknowledgment cap from 64 to 128** — a wide-touching maintenance PR could legitimately accumulate more distinct commit-trailer acknowledgments than the old ceiling allowed, failing CI even though nothing was wrong. (#4058)

tests/helpers/emitted-diff.cjs

@@ -646,7 +646,7 @@ function formatReport(result, { sampleLimit = 20 } = {}) {
  */
 
 /** Upper bound on trailers read from one range. Real implementation throws above this. */
-const MAX_ACK_TRAILERS = 64;
+const MAX_ACK_TRAILERS = 128;
 
 /**
  * Parse trailer VALUES already extracted per trailer name (no git I/O — the two