test(docker): derive image contract from pinned Node version

src/lib/docker-build-contract.test.ts

@@ -37,7 +37,8 @@ it("passes a compiled release to both the application build and final image", ()
 	expect(dockerfile).toContain(
 		'LABEL org.opencontainers.image.revision="$NEXT_DEPLOYMENT_ID"',
 	);
-	expect(dockerfile.match(/FROM node:26\.8\.1-alpine/g)).toHaveLength(2);
+	const pinnedNode = readFileSync(".nvmrc", "utf8").trim();
+	expect(dockerfile.split(`FROM node:${pinnedNode}-alpine`).length - 1).toBe(2);
 	const compose = readFileSync("docker-compose.yml", "utf8");
 	// biome-ignore lint/suspicious/noTemplateCurlyInString: Docker Compose interpolation, not JavaScript.
 	expect(compose).toContain("NEXT_DEPLOYMENT_ID: ${CMS_RELEASE:-unknown}");