1 s of 440 Hz sine + 10 broadband clicks → stft(1024, 256) →
magnitude → hpss(). The horizontal 440 Hz line must land in the
harmonic panel, the vertical click stripes in the percussive panel. Badges
mirror examples/node/decompose-hpss.mjs: 440 Hz-bin dominance,
click-column dominance, margin=1 complementarity (H + P == S per bin),
masks summing to exactly 1, and the power=∞ strict 0/1 hard mask.