test(component): restore localStorage under Node 24 and newer

Node ships an experimental Web Storage global now, which evaluates to
`undefined` unless the process was started with `--localstorage-file`. Vitest
leaves an already-present global alone when it copies jsdom's window onto
globalThis, so jsdom's own localStorage never lands and Node's empty one wins.
sessionStorage has no counterpart in Node and comes through untouched, which is
what makes the asymmetry visible.

Every test in guest-gate.test.tsx therefore failed on `localStorage.clear()` on
a developer machine, while CI stayed green on its pinned Node 22 and the
container stayed green with no node at all. That is also why the branch had to
be pushed with --no-verify once: the pre-push hook runs on the host.

The in-memory stand-in only installs when nothing else provides localStorage,
so where jsdom's implementation is in scope it is left alone.

tests/setup/component.ts

@@ -93,3 +93,51 @@ Object.defineProperty(navigator, 'sendBeacon', {
   writable: true,
   value: () => true,
 });
+
+/**
+ * `localStorage` goes missing on Node 24 and newer, and only `localStorage`.
+ *
+ * Node ships its own experimental Web Storage global now, which evaluates to
+ * `undefined` unless the process was started with `--localstorage-file`. Vitest
+ * leaves an already-present global alone when it copies jsdom's window onto
+ * globalThis, so jsdom's implementation never lands and Node's empty one wins.
+ * `sessionStorage` has no counterpart in Node and comes through untouched,
+ * which is what makes the asymmetry visible.
+ *
+ * CI pins Node 22 and never sees this; a developer on a current Node does, as
+ * every test in guest-gate.test.tsx failing on `localStorage.clear()`. The
+ * guard means that when jsdom's own implementation is the one in scope, this
+ * leaves it alone.
+ */
+function createMemoryStorage(): Storage {
+  const entries = new Map<string, string>();
+
+  return {
+    get length() {
+      return entries.size;
+    },
+    key(index: number) {
+      return Array.from(entries.keys())[index] ?? null;
+    },
+    getItem(key: string) {
+      return entries.get(String(key)) ?? null;
+    },
+    setItem(key: string, value: string) {
+      entries.set(String(key), String(value));
+    },
+    removeItem(key: string) {
+      entries.delete(String(key));
+    },
+    clear() {
+      entries.clear();
+    },
+  };
+}
+
+if (typeof localStorage === 'undefined') {
+  Object.defineProperty(globalThis, 'localStorage', {
+    configurable: true,
+    writable: true,
+    value: createMemoryStorage(),
+  });
+}