fix: expose physical aliasing and delayed arrivals

apps/dataset-builder/model.js

@@ -1,3 +1,5 @@
+import { describeFrequencyAliasing } from "/packages/acoustics-core/sampling.js";
+
 export const DEFAULT_VIEW_PLANE = Object.freeze({
   xMin: -0.6,
   xMax: 0.6,
@@ -192,8 +194,20 @@ export function changeSignalType(source, type, firstAudioAssetId = "") {
   }
 }
 
-export function describeSignal(signal) {
-  if (signal.type === "tone") return `${signal.frequency} Hz tone`;
+export function describeSignal(signal, sampleRate) {
+  if (signal.type === "tone") {
+    if (!Number.isFinite(sampleRate)) return `${signal.frequency} Hz tone`;
+    const observation = describeFrequencyAliasing(signal.frequency, sampleRate);
+    const alias = observation.aliased
+      ? ` → ADC ${observation.adcFrequencyHz} Hz alias`
+      : "";
+    const edge = observation.dcEdge
+      ? " · DC phase-degenerate edge"
+      : observation.nyquistEdge
+        ? " · Nyquist phase-degenerate edge"
+        : "";
+    return `${signal.frequency} Hz tone${alias}${edge}`;
+  }
   if (signal.type === "noise") return `${signal.color} noise`;
   if (signal.type === "asset") return `asset · ${signal.assetId || "미선택"}`;
   return "알 수 없는 신호";