The counter is the denominator of the very period lastAccHrt is the
numerator of, so any packet that cannot move the tick reference must not
move the counter either. Two paths were violating that: a reordered
datagram rolled the counter back while the reference correctly held
(next burst drawn 0.048x too narrow at distance 20, 83.3% worst spacing
error under 2% sustained reordering), and a stray hrt == 0 packet
advanced the counter from the warm-up branch without a tick to match
(+22.5 ms of future-dating per stray packet).
Rules 1 and 2 now record a counter too. The duplicate-datagram guard is
keyed on one, so an array rule that recorded none was exempt and plotted
every doubly-delivered update twice.
Also: rule 2 divides by the count the anchor actually spans and falls
back to the last period it derived; the counter-gap test is wrap-safe so
2^32 rollover reads as no information rather than 2e9 lost packets.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
