fix: harden beam pattern numerical diagnostics

tests/unit/beam-pattern.test.js

@@ -95,13 +95,28 @@ test("half-wavelength two-microphone broadside cut has nulls, 60-degree HPBW, an
   assertNear(sampleAtAngle(pattern, 270), 0, 1e-12, "endfire null at -x");
   assertNear(sampleAtAngle(pattern, 0), 1, 1e-12, "steered broadside response");
   assertNear(sampleAtAngle(pattern, 180), 1, 1e-12, "planar front-back response");
-  assertEqual(pattern.metrics.halfPowerBeamwidth.status, "bounded", "HPBW status");
+  assertEqual(
+    pattern.metrics.halfPowerBeamwidth.status,
+    "sampled-bracketed-bisection",
+    "HPBW status",
+  );
   assertNear(pattern.metrics.halfPowerBeamwidth.widthDeg, 60, 1e-10, "power HPBW");
   const zeroDbAngles = pattern.metrics.sampledLocalMaxima.peaks
     .filter((peak) => Math.abs(peak.responseDb) < 1e-10)
     .map((peak) => peak.angleDeg)
     .sort((left, right) => left - right);
   assertEqual(zeroDbAngles.join(","), "0,180", "front-back maxima remain tied");
+  assertEqual(
+    pattern.metrics.sampledLocalMaxima.status,
+    "tied-global-maxima-on-grid",
+    "global tie is explicit",
+  );
+  assertEqual(pattern.metrics.sampledLocalMaxima.selected, null, "tie has no selected peak");
+  assertEqual(
+    pattern.metrics.sampledLocalMaxima.globalMaximumRegions.length,
+    2,
+    "both tied regions are preserved",
+  );
   assertNear(pattern.responseReal[Math.floor(pattern.sampleCount / 2)], 1, 1e-12, "raw real");
   assertNear(pattern.responseImaginary[Math.floor(pattern.sampleCount / 2)], 0, 1e-12, "raw imaginary");
   assertNear(pattern.responsePower[Math.floor(pattern.sampleCount / 2)], 1, 1e-12, "raw power");
@@ -258,6 +273,33 @@ test("coarse high-frequency cuts preserve raw samples but withhold unresolved me
   assertEqual(pattern.responsePower.length, 360, "raw sampled power remains available");
 });
 
+test("non-constant cuts without sampled half-power crossings do not claim 360-degree HPBW", () => {
+  const pattern = computeReceiveBeamPattern({
+    array: arrayFromPositions([[-0.0005, 0, 0], [0.0005, 0, 0]]),
+    frequencyHz: 1_000,
+    speedOfSound: 343,
+    cut: "xz",
+    steeringAngleDeg: 0,
+    sampleCount: 720,
+  });
+  assert(pattern.angularSampling.projectedApertureM > 0, "array is not constant on cut");
+  assert(
+    Math.min(...pattern.responsePower) > 0.5,
+    "sampled cut stays above half power",
+  );
+  assertEqual(
+    pattern.metrics.halfPowerBeamwidth.status,
+    "no-sampled-half-power-crossing",
+    "missing crossing remains unresolved",
+  );
+  assertEqual(pattern.metrics.halfPowerBeamwidth.widthDeg, null, "no fabricated width");
+  assertEqual(
+    pattern.metrics.halfPowerBeamwidth.fullCircleAboveHalfPower,
+    null,
+    "full-circle claim is withheld",
+  );
+});
+
 test("auto angular sampling increases resolution and reports when the safety cap is insufficient", () => {
   const moderate = computeReceiveBeamPattern({
     array: arrayFromPositions([[-0.225, 0, 0], [0.225, 0, 0]]),
@@ -324,4 +366,26 @@ test("beam-pattern preflight rejects invalid input and excessive work", () => {
     microphoneLimitError.message.includes("1024"),
     "microphone cap is explicit",
   );
+
+  let baselineError = null;
+  try {
+    computeReceiveBeamPattern({
+      array,
+      frequencyHz: 1_000,
+      maximumBaselineComparisons: 0,
+    });
+  } catch (error) {
+    baselineError = error;
+  }
+  assert(baselineError instanceof RangeError, "baseline pair cap is checked");
+  assert(baselineError.message.includes("1 projected-baseline"), "pair work is explicit");
+
+  let frequencyLimitError = null;
+  try {
+    computeReceiveBeamPattern({ array, frequencyHz: 1_000_001 });
+  } catch (error) {
+    frequencyLimitError = error;
+  }
+  assert(frequencyLimitError instanceof RangeError, "extreme analog frequency is bounded");
+  assert(frequencyLimitError.message.includes("1000000"), "frequency cap is explicit");
 });