fix: expose physical aliasing and delayed arrivals

packages/acoustics-core/stft.js

@@ -1,5 +1,6 @@
 import { fftInPlace } from "./fft.js";
 import { cooperativeYield } from "./cooperative-yield.js";
+import { observeFrequencyBand } from "./sampling.js";
 
 function throwIfAborted(signal) {
   if (signal?.aborted) {
@@ -119,11 +120,5 @@ export async function extractStftBins(channels, options) {
 }
 
 export function binsForBand(band, sampleRate, fftSize) {
-  const binWidth = sampleRate / fftSize;
-  const firstBin = Math.max(0, Math.ceil(band.minHz / binWidth));
-  const lastBin = Math.min(fftSize / 2, Math.floor(band.maxHz / binWidth));
-  if (firstBin > lastBin) {
-    throw new Error(`${band.minHz}–${band.maxHz} Hz에 해당하는 FFT bin이 없습니다.`);
-  }
-  return Array.from({ length: lastBin - firstBin + 1 }, (_, index) => firstBin + index);
+  return observeFrequencyBand(band, sampleRate, fftSize).bins;
 }