fix(bridge): fix TypeScript errors in tests and command handler

- Add qs() helper for type-safe element queries in happy-dom tests
- Make comms-url handler async to match registerCommand signature
- Downgrade require-await to warning (async-without-await is required
  by some pi API signatures)
- Add test/helpers.ts to ESLint test file overrides
- Guard indexed access with assert.ok before property access

Author: Mearman

src/bridges/user/web/frontend/test/helpers.ts

@@ -0,0 +1,21 @@
+/**
+ * Shared test helpers for frontend component tests.
+ */
+
+/**
+ * Query selector that returns HTMLElement.
+ * Throws if element not found. Uses type narrowing suitable for
+ * happy-dom (where elements are not instanceof HTMLElement).
+ */
+export function qs(parent: ParentNode, selector: string): HTMLElement {
+  const el = parent.querySelector(selector);
+  if (el === null) {
+    throw new Error(`HTMLElement not found: ${selector}`);
+  }
+  if ("click" in el && "style" in el) {
+    return el as HTMLElement;
+  }
+  throw new Error(
+    `Element ${selector} is not an HTMLElement: ${el.constructor.name}`,
+  );
+}