Saturalabs pitch-preserving speed listening example

Source: ../tap-tempo/120-bpm.wav, an original eight-second synthetic reference.
Processed file: 120-bpm-at-075x.wav, generated at 0.750x by the actual
application's prepareAudioSpeed function, module worker, and PCM WAV writer.

Reproduce from the repository:
  node --import tsx scripts/generate-speed-listening-example.mjs
Requires FFmpeg and FFprobe. A Node worker-thread bridge invokes the same
public worker module as the browser tool. No browser automation is used.

The output is mono 48000 Hz 16-bit PCM WAV, 512000 frames, 1024044 bytes,
10.666666667 seconds. This particular file has no extra retained tail.
Nominal tempo is 90 BPM (120 times 0.75). That number is arithmetic, not a
measured beat-tracker result. Pitch preservation does not mean lossless audio.
The synthetic example does not establish vocal, musical, or transient quality.

Verification records: docs/experiments/speed-listening-example.json.
FFmpeg independently decodes the saved WAV; the generator checks format,
frame count, finite nonzero samples, byte count, and unchanged source hash.
These checks do not verify browser playback or human listening outcomes.

Copyright: Saturalabs. Only the original tap-tempo/120-bpm.wav and this
speed/120-bpm-at-075x.wav are dedicated under CC0 1.0:
https://creativecommons.org/publicdomain/zero/1.0/
Other audio, site media, and software have their own licenses.