perf: enforce journey budgets and reference traces

scripts/lib/performance-aggregation.mjs

@@ -0,0 +1,37 @@
+const median = (values) => {
+  if (values.length === 0) throw new Error('At least one value is required.');
+  const sorted = [...values].sort((left, right) => left - right);
+  return sorted[Math.floor(sorted.length / 2)];
+};
+
+export const aggregateFiveDriveTraces = (runs) => {
+  if (!Array.isArray(runs) || runs.length !== 5) throw new Error('Exactly five drive-trace.v1 runs are required.');
+  const profile = runs[0]?.profile;
+  if (typeof profile !== 'string' || runs.some((run) => run?.schema !== 'drive-trace.v1' || run.profile !== profile)) {
+    throw new Error('All runs must use one drive-trace.v1 profile.');
+  }
+  const lcp = runs.map((run) => run.metrics.lcp);
+  const tbt = runs.map((run) => run.metrics.tbt);
+  const everyPerRunBudgetPass = runs.every((run) => Object.values(run.budgetResults).every(Boolean));
+  const referenceEvidence = runs.every((run) => run.gatingReferenceResult === true && run.validReferenceCadence === true);
+  const summary = {
+    lcpWorst: Math.max(...lcp),
+    lcpMedian: median(lcp),
+    tbtWorst: Math.max(...tbt),
+    tbtMedian: median(tbt),
+    everyPerRunBudgetPass,
+    referenceEvidence,
+  };
+  return {
+    schema: 'drive-trace-aggregation/v1',
+    profile,
+    runCount: 5,
+    summary,
+    passes: referenceEvidence
+      && everyPerRunBudgetPass
+      && summary.lcpWorst <= 3_000
+      && summary.lcpMedian <= 2_500
+      && summary.tbtWorst <= 300
+      && summary.tbtMedian <= 200,
+  };
+};