chore: codify frontend local verification

scripts/verify-node-version.mjs

@@ -0,0 +1,28 @@
+import { readFileSync } from "node:fs";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const root = resolve(dirname(fileURLToPath(import.meta.url)), "..");
+const packageJson = JSON.parse(
+	readFileSync(resolve(root, "package.json"), "utf8"),
+);
+const nvmVersion = readFileSync(resolve(root, ".nvmrc"), "utf8").trim();
+const expectedMajor = nvmVersion.replace(/^v/, "").split(".")[0];
+const expectedEngine = `${expectedMajor}.x`;
+
+if (packageJson.engines?.node !== expectedEngine) {
+	throw new Error(
+		`Node runtime contracts disagree: .nvmrc=${nvmVersion}, package.json engines.node=${packageJson.engines?.node ?? "missing"}`,
+	);
+}
+
+const actualVersion = process.versions.node;
+const actualMajor = actualVersion.split(".")[0];
+if (actualMajor !== expectedMajor) {
+	console.error(
+		`Unsupported Node.js runtime: expected ${expectedEngine}, actual ${actualVersion}. Activate .nvmrc before running repository checks.`,
+	);
+	process.exit(1);
+}
+
+console.log(`Node.js runtime verified: ${actualVersion} (${expectedEngine})`);