feat: tune multi-source peak sensitivity

tests/unit/contracts.test.js

@@ -61,6 +61,35 @@ test("단일 tone 장면과 실험이 관계 검증을 통과한다", async () =
   assertEqual((await validateExperiment(experiment, { arrayDefinition, scene })).length, 0, "experiment issues");
 });
 
+test("Experiment 피크 검출 임계값 비율은 재현 가능하고 유효한 범위여야 한다", async () => {
+  const [arrayDefinition, scene, experiment] = await Promise.all([
+    loadJson("/assets/array-geometries/rectangular-16x12.array.json"),
+    loadJson("/assets/sample-scenes/single-tone.scene.json"),
+    loadJson("/assets/sample-scenes/single-tone.experiment.json"),
+  ]);
+  assertEqual(experiment.evaluation.detectionThresholdRatio, 0.25, "sample threshold ratio");
+  assertEqual(
+    (await validateExperiment(experiment, { arrayDefinition, scene })).length,
+    0,
+    "0.25 threshold issues",
+  );
+
+  experiment.evaluation.detectionThresholdRatio = 0;
+  let issues = await validateExperiment(experiment, { arrayDefinition, scene });
+  assert(
+    issues.some(({ path, message }) =>
+      path === "$.evaluation.detectionThresholdRatio" && message.includes("0보다 크고 1 이하")),
+    "zero threshold is rejected with actionable guidance",
+  );
+
+  experiment.evaluation.detectionThresholdRatio = 1.01;
+  issues = await validateExperiment(experiment, { arrayDefinition, scene });
+  assert(
+    issues.some(({ path }) => path === "$.evaluation.detectionThresholdRatio"),
+    "threshold above one is rejected",
+  );
+});
+
 test("이동 음원 trajectory의 keyframe 순서와 장면 시간 범위를 검증한다", async () => {
   const scene = await loadJson("/assets/sample-scenes/single-tone.scene.json");
   scene.sources[0].trajectory = [