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/useFilesViewTabsStore.ts

@@ -1,7 +1,7 @@
 import { create } from 'zustand';
-import { createJSONStorage, devtools, persist } from 'zustand/middleware';
+import { devtools, persist } from 'zustand/middleware';
 
-import { getSafeStorage } from './utils/safeStorage';
+import { createDeferredSafeJSONStorage } from './utils/safeStorage';
 
 type RootTabsState = {
   openPaths: string[];
@@ -451,7 +451,7 @@ export const useFilesViewTabsStore = create<FilesViewTabsStore>()(
       {
         name: 'files-view-tabs-store',
         version: 2,
-        storage: createJSONStorage(() => getSafeStorage()),
+        storage: createDeferredSafeJSONStorage(),
         migrate: (persistedState) => {
           if (!persistedState || typeof persistedState !== 'object') {
             return { byRoot: {} };