perf(stores): defer safeStorage writes off the interaction path (#1941)

* perf(stores): defer safeStorage writes off the interaction path

Session switches funnel every persisted store slice through safeStorage.setItem,
and doing those large JSON.stringify writes synchronously blocked the main
thread for over a second. Add a write-behind buffer that:

- Defers each setItem/removeItem to a later task via setTimeout(0) so the
  click-to-paint path is not blocked.
- Coalesces repeated writes to the same key into a single backing flush.
- Serves pending values from memory so read-after-write stays consistent
  within the deferral window.
- Flushes synchronously on pagehide/beforeunload/visibilitychange/freeze so
  deferred state survives tab close, reload, and the mobile freeze lifecycle.

Adds a test covering write deferral, coalescing, and pending read serving.

* fix(stores): defer persisted JSON serialization

* fix(stores): defer direct safeStorage writes

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/stores/messageQueueStore.ts

@@ -1,6 +1,6 @@
 import { create } from 'zustand';
-import { devtools, persist, createJSONStorage } from 'zustand/middleware';
-import { getSafeStorage } from './utils/safeStorage';
+import { devtools, persist } from 'zustand/middleware';
+import { createDeferredSafeJSONStorage } from './utils/safeStorage';
 import type { AttachedFile } from './types/sessionTypes';
 import { updateDesktopSettings } from '@/lib/persistence';
 
@@ -201,7 +201,7 @@ export const useMessageQueueStore = create<MessageQueueStore>()(
             {
                 name: 'message-queue-store',
                 version: 1,
-                storage: createJSONStorage(() => getSafeStorage()),
+                storage: createDeferredSafeJSONStorage(),
                 partialize: (state) => ({
                     queuedMessages: state.queuedMessages,
                     followUpBehavior: state.followUpBehavior,