Merge branch 'fix/pre-existing-test-failures'

Triage and fix of 12 pre-existing test failures on main (flagged by
the #10 DM origin failover merge, commit ff39ab0).

Two root causes:

1. Node 20+'s built-in localStorage/sessionStorage stub shadows jsdom's
   working implementation because vitest's populateGlobal doesn't
   overwrite globals outside its known allow-list. Any zustand persist
   store threw "storage.setItem is not a function". Polyfilled with an
   in-memory Storage in src/test/setup.ts. Resolves 11 of 12 failures
   (10 keybindStore + 1 FriendsPage toast).

2. FriendsPage "Message button" DM test carried a stale two-arg
   assertion that predated the 2026-04-01 federation refactor (commit
   7f3ca4e) which dropped the second argument from addDmChannel.
   Dropped the trailing '' so the assertion matches current behavior.

Hand-backs (not touched on this branch):
- InviteModal.test.tsx and JoinSpace.test.tsx still fail to LOAD (not
  in the 12 tests but flagged by #10's merge note). After stubbing
  AudioManager a second blocker surfaces: TDZ error on _getApiForOrigin
  in spaceStore.ts:961, caused by a circular-import init order between
  spaceStore and instanceStore (via socialStore → useWebSocket →
  voiceStore). Federation-adjacent — filed as backlog item for a
  structural fix.

Server: 90/90 unchanged.  Web: 121/121 pass (was 109/121), 2 suite
loads still failing (tracked).

packages/web/src/components/chat/FriendsPage.test.tsx

@@ -322,7 +322,7 @@ describe('FriendsPage', () => {
       });
 
       await waitFor(() => {
-        expect(mockAddDmChannel).toHaveBeenCalledWith(expect.objectContaining({ id: 'dm-channel-99' }), '');
+        expect(mockAddDmChannel).toHaveBeenCalledWith(expect.objectContaining({ id: 'dm-channel-99' }));
       });
 
       await waitFor(() => {

packages/web/src/test/setup.ts

@@ -1,5 +1,40 @@
 import '@testing-library/jest-dom/vitest';
 
+// Node 20+ ships a built-in `localStorage`/`sessionStorage` stub on globalThis
+// that has no methods unless `--localstorage-file=PATH` is provided. Vitest's
+// jsdom env only overwrites globals it knows about, and neither storage is in
+// that list — so Node's broken stub shadows jsdom's working implementation,
+// breaking anything that persists via zustand's `persist` middleware.
+// Replace both with an in-memory Storage-compatible polyfill.
+class InMemoryStorage implements Storage {
+  private store = new Map<string, string>();
+  get length(): number {
+    return this.store.size;
+  }
+  clear(): void {
+    this.store.clear();
+  }
+  getItem(key: string): string | null {
+    return this.store.has(key) ? this.store.get(key)! : null;
+  }
+  key(index: number): string | null {
+    return Array.from(this.store.keys())[index] ?? null;
+  }
+  removeItem(key: string): void {
+    this.store.delete(key);
+  }
+  setItem(key: string, value: string): void {
+    this.store.set(key, String(value));
+  }
+}
+for (const name of ['localStorage', 'sessionStorage'] as const) {
+  Object.defineProperty(globalThis, name, {
+    value: new InMemoryStorage(),
+    configurable: true,
+    writable: true,
+  });
+}
+
 // Polyfill ClipboardItem for jsdom (not included in jsdom)
 if (typeof ClipboardItem === 'undefined') {
   // eslint-disable-next-line @typescript-eslint/no-explicit-any