fix(ui): convert node stubs to plain JavaScript

Biome flagged TypeScript syntax in the .mjs stub module. Remove type
annotations and prefix the unused run() store parameter with underscore
to satisfy lint rules.

e2e/ui/node-stubs.mjs

@@ -2,18 +2,18 @@
 // UI fixture bundle. These keep esbuild from failing on `node:*` imports
 // while providing shape-compatible exports so the bundle stays loadable.
 
-export class AsyncLocalStorage<T = unknown> {
-	enterWith(): void {}
-	exit(): void {}
-	getStore(): T | undefined {
+export class AsyncLocalStorage {
+	enterWith() {}
+	exit() {}
+	getStore() {
 		return undefined;
 	}
-	run<U>(store: T, work: () => U): U {
+	run(_store, work) {
 		return work();
 	}
 }
 
-export function createHash(): { update(): { digest(): string } } {
+export function createHash() {
 	return {
 		update: () => ({
 			digest: () => "",
@@ -21,16 +21,16 @@ export function createHash(): { update(): { digest(): string } } {
 	};
 }
 
-export function randomUUID(): string {
+export function randomUUID() {
 	return "00000000-0000-0000-0000-000000000000";
 }
 
-export async function readFile(): Promise<Buffer> {
+export async function readFile() {
 	return Buffer.alloc(0);
 }
 
 export const path = {
-	join: (...parts: string[]): string => parts.join("/"),
-	resolve: (...parts: string[]): string => parts.join("/"),
+	join: (...parts) => parts.join("/"),
+	resolve: (...parts) => parts.join("/"),
 	sep: "/",
 };