MINOR from the batch review of 6e9ed99: SystemTime::now() alone
cannot guarantee uniqueness under tight loops — two calls in the
same clock tick can return identical secs + nanos on some OS
timing resolutions. The filename reduction from "every second"
to "every nanosecond" addresses the flagged bug but leaves a
theoretical gap.
Adds a process-lifetime AtomicU64 counter, zero-padded to 4 digits,
as the third filename component. New shape:
kon-<secs>-<nanos_in_sec>-<counter>.wav
e.g. kon-1776828000-123456789-0000.wav
Across process restarts the counter resets to 0, but the wall-clock
secs/nanos have advanced — no cross-launch collisions possible.
Within a single process, the counter guarantees uniqueness regardless
of clock behaviour.
Test strengthened from ">=32 of 64 unique" (probabilistic) to
"1024 of 1024 unique" (absolute).