Load a beat, see its waveform, loop a slice of it — the three basics every
audio app needs, working together on one page. Press run and the marked
quarter of the track plays on a seamless loop while the page checks itself.
Technically it exercises all three exports on the 15 s golden WAV:
loadAudioFile (with its URL cache), drawWaveform
(loop overlay {0.25, 0.5}), and initAudioProcessor playing the
native looped region. Badges: loop duration exactly 0.25 × duration
(3.750 s for the 15 s file), 20/20 playhead samples inside [0.25, 0.5],
cache identity (second load returns the === same AudioBuffer), and pixel
probes proving the loop markers paint at x = 0.25·width and 0.5·width.
press run