fix: expose physical aliasing and delayed arrivals

apps/dataset-builder/index.html

@@ -150,7 +150,7 @@
                 </div>
               </section>
               <label class="field field--wide"><span>신호 종류</span><select id="source-type"><option value="tone">Tone</option><option value="noise">Noise</option><option value="asset">Audio asset</option></select></label>
-              <div id="tone-fields"><label class="field field--wide"><span>주파수 (Hz)</span><input id="tone-frequency" type="number" min="1" step="1" /></label></div>
+              <div id="tone-fields"><label class="field field--wide" title="Nyquist를 넘어도 허용됩니다. 0–1 MHz는 현재 수치·마이크 모델의 검증 범위이며, 이상적 anti-alias filter 없는 ADC에서 접힌 주파수는 source 카드에 표시됩니다."><span>아날로그 tone 주파수 (Hz)</span><input id="tone-frequency" type="number" min="1" max="1000000" step="1" /></label></div>
               <div id="noise-fields"><label class="field field--wide"><span>Noise color</span><select id="noise-color"><option value="white">White</option><option value="pink">Pink</option></select></label></div>
               <div id="asset-fields">
                 <label class="field field--wide"><span>Audio asset</span><select id="source-asset"></select></label>