refactor: validate generated evidence artifacts

scripts/test-performance.ts

@@ -1,5 +1,5 @@
 import { spawn } from "node:child_process";
-import { mkdir, readFile, writeFile } from "node:fs/promises";
+import { mkdir, readFile } from "node:fs/promises";
 import { performance } from "node:perf_hooks";
 import process from "node:process";
 
@@ -7,6 +7,8 @@ import { chromium } from "@playwright/test";
 
 import { evaluateLabBudget } from "../src/application/policies/performance-budgets.ts";
 import { ROUTE_REGISTRY } from "../src/features/installed-feature-contracts.ts";
+import { labPerformanceArtifactSchema } from "./contracts/release-artifacts.ts";
+import { writeValidatedJsonArtifact } from "./lib/validated-json-artifact.ts";
 
 type ContractPerformanceEvidence = {
   lcpMs: number;
@@ -142,22 +144,19 @@ try {
     ];
     const passed = result.passed && fixtures.every((fixture) => fixture.passed);
     await mkdir("artifacts/performance", { recursive: true });
-    await writeFile(
-      "artifacts/performance/lab.json",
-      `${JSON.stringify(
-        {
-          schemaVersion: 1,
-          generatedAt: new Date().toISOString(),
-          context: contextMetadata,
-          metrics,
-          thresholds,
-          fixtures,
-          passed,
-        },
-        null,
-        2,
-      )}\n`,
-    );
+    await writeValidatedJsonArtifact({
+      path: "artifacts/performance/lab.json",
+      schema: labPerformanceArtifactSchema,
+      value: {
+        schemaVersion: 1,
+        generatedAt: new Date().toISOString(),
+        context: contextMetadata,
+        metrics,
+        thresholds,
+        fixtures,
+        passed,
+      },
+    });
     if (!passed) {
       throw new Error(`Lab performance failed: ${JSON.stringify(metrics)}`);
     }