The prefix, AS and peer handlers skipped a timed write unless one
interval had passed since the last write ended. The next tick came a
little less than one interval after that, so every other tick was
skipped. Each tick now writes. A full batch's write restarts the timer,
so the next timed write comes one interval after that write began.
Comparing clock readings would not do: two ticks one interval apart can
read a hair under it. flushBatch no longer reports whether it wrote a
batch, since nothing reads that. A new test runs the loop on a fake
clock and fails on the old code.
Model: opus-5-5