feat: visualize beam spread around peaks

tests/unit/camera.test.js

@@ -191,6 +191,22 @@ test("Camera result document is schema-safe and linked to its snapshot", async (
       value: 1,
       localizationErrorM: 0.05,
       localizationErrorPixels: 0.1,
+      beamSpread: {
+        calibrated: false,
+        method: "connected-half-power-power-weighted-covariance",
+        halfPowerRatio: 0.5,
+        thresholdValue: 0.5,
+        pixelCount: 3,
+        centroid: [0.9, -0.9, 2],
+        covarianceM2: { xx: 0.04, xy: 0.01, yy: 0.02 },
+        ellipse: {
+          axisScale: "rms",
+          angleReference: "counterclockwise-from-positive-x",
+          majorRmsRadiusM: 0.21,
+          minorRmsRadiusM: 0.12,
+          angleDeg: 22.5,
+        },
+      },
     }],
     metrics: {
       peakToSidelobeDb: 10,
@@ -232,6 +248,8 @@ test("Camera result document is schema-safe and linked to its snapshot", async (
     "only finite schema metrics are exported",
   );
   assertEqual(result.bands[0].peaks[0].localizationErrorPixels, 0.1, "pixel error is exported");
+  assertEqual(result.bands[0].peaks[0].beamSpread.pixelCount, 3, "beam spread is exported");
+  assertEqual(result.bands[0].peaks[0].beamSpread.calibrated, false, "beam spread is not probability");
   assertEqual(result.bands[0].evaluation.matchToleranceM, 0.2, "evaluation settings are exported");
   assertEqual(result.environment.scanXMin, -1, "scan bounds are recorded");
   assertEqual(result.environment.fallbackCode, "webgpu-unavailable", "fallback is recorded");