v0.39.0

Fixed

• AckLatencyEstimator.AckIntervalSeconds read the snapshot cadence 25% low; it now measures
  over a ring of gaps. 0.35.0 recorded this as measured-and-unfixed and pinned the two wrong
  readings as tests so the next attempt had to come past them. It does: 63.889 ms against a true
  66.667 on the same jitter fixture (4.2% low, where it read 50.000 ms) and exactly 66.667 on an
  ideal cadence. The cadence fallback is now visible and counted rather than silent.

• PredictionLatencyMeasurement gates on the correction RATE, not the max. The max over ~28
  corrections is one draw from a tail, and it was the statistic being asserted — a run failed on
  max correction 2.00 steps while corrections > ONE STEP read 1 of 28 and passed comfortably.
  One event is not a trend, and the assertion that fired could not tell them apart. The max is
  still computed and still printed with its full explanatory message, now as a warning: a
  reporting threshold rather than a budget.

These five commits sat on fix/intervalstat from 2026-09-09 with no pull request ever
opened, and were found by sweeping every branch unreachable from main. Five other branches
turned up the same way and none of them was merged — each was verified as already-landed
content on a stale fork. The detailed entries, and the in-place corrections to the 0.35.0/0.36.0
text they falsify, are filed beside the claims they correct, per this file's convention.