fix: stabilize localization comparison semantics

tests/integration/webgpu.test.js

@@ -118,6 +118,38 @@ test("WebGPU DAS가 CPU 수치 기준과 일치하거나 auto CPU fallback한다
   document.documentElement.dataset.webgpuRmsError = error.rms.toExponential(3);
 });
 
+test("WebGPU DAS-PHAT가 CPU score map과 일치하거나 auto CPU fallback한다", async () => {
+  const adapter = await globalThis.navigator?.gpu?.requestAdapter();
+  const fixture = createFixture(adapter ? "webgpu" : "auto");
+  fixture.experiment.beamforming.algorithm = "das-phat";
+  fixture.experiment.frequencyBands = [
+    { id: "phase-1k", minHz: 900, maxHz: 1_100, color: "#65f2bf" },
+  ];
+
+  if (!adapter) {
+    const result = await computeDasWithBackend(fixture);
+    assertEqual(result.backend, "cpu", "DAS-PHAT auto fallback backend");
+    assertEqual(result.algorithm, "das-phat", "DAS-PHAT fallback algorithm");
+    assertEqual(result.bands[0].rawScale, "score", "DAS-PHAT fallback scale");
+    return;
+  }
+
+  const cpuResult = await computeDasMap(fixture);
+  const gpuResult = await computeDasWebGpu(fixture);
+  const cpuBand = cpuResult.bands[0];
+  const gpuBand = gpuResult.bands[0];
+  const error = normalizedMapError(cpuBand.rawMap, gpuBand.rawMap);
+
+  assertEqual(gpuResult.algorithm, "das-phat", "actual WebGPU DAS-PHAT algorithm");
+  assertEqual(gpuBand.rawScale, "score", "actual WebGPU DAS-PHAT scale");
+  assert(!("rawPower" in gpuBand.peak), "DAS-PHAT GPU peak is not mislabeled as power");
+  assert(error.rms <= 0.005, `DAS-PHAT CPU/GPU normalized RMS error=${error.rms}`);
+  assert(
+    error.maximumAbsoluteError <= 0.02,
+    `DAS-PHAT CPU/GPU normalized max error=${error.maximumAbsoluteError}`,
+  );
+});
+
 test("192채널 · 50×50 WebGPU map이 CPU baseline 허용 오차를 만족한다", async () => {
   const adapter = await globalThis.navigator?.gpu?.requestAdapter();
   if (!adapter) {