fix: restore workflow tabs on browser restart (#10336)

## Problem

Since PR #8520 (`feat(persistence): fix QuotaExceededError and
cross-workspace draft leakage`), all workflow tabs are lost when the
browser is closed and reopened.

PR #8520 moved tab pointers (`ActivePath`, `OpenPaths`) from
`localStorage` to `sessionStorage` for per-tab isolation. However,
`sessionStorage` is cleared when the browser closes, so the open tab
list is lost on restart. The draft data itself survives in
`localStorage` — only the pointers to which tabs were open are lost.

Reported in
[Comfy-Org/ComfyUI#12984](https://github.com/Comfy-Org/ComfyUI/issues/12984).
Confirmed via binary search: v1.40.9 (last good) → v1.40.10 (first bad).

## Changes

Dual-write tab pointers to both storage layers:

- **sessionStorage** (scoped by `clientId`) — used for in-session
refresh, preserves per-tab isolation
- **localStorage** (scoped by `workspaceId`) — fallback for browser
restart when sessionStorage is empty

Also adds:
- `storageAvailable` guard on write functions for consistency with
`writeIndex`/`writePayload`
- `isValidPointer` validation on localStorage reads to reject stale or
malformed data

## Benefits

- Workflow tabs survive browser restart (restores V1 behavior)
- Per-tab isolation is preserved for in-session use (sessionStorage is
still preferred when available)

## Trade-offs

- On browser restart, the restored tabs come from whichever browser tab
wrote last to localStorage. If Tab A had workflows 1,2,3 and Tab B had
4,5 — the user gets whichever tab wrote most recently. This is the same
limitation V1 had with `Comfy.OpenWorkflowsPaths` in localStorage.
- Previously (post-#8520), opening a new browser tab would only restore
the single most recent draft. With this fix, a new tab restores the full
set of open tabs from the last session. This may be surprising for
multi-tab users who expect a clean slate in new tabs.

## Test plan

- [x] `pnpm typecheck` passes
- [x] `pnpm lint` passes
- [x] All 121 persistence tests pass
- [x] Manual: open multiple workflow tabs → close browser → reopen →
tabs restored
- [x] Manual: open two browser tabs with different workflows → refresh
each → correct tabs in each

Fixes Comfy-Org/ComfyUI#12984

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10336-fix-restore-workflow-tabs-on-browser-restart-3296d73d365081b7a7d3e91427d08d17)
by [Unito](https://www.unito.io)
<!-- QA_REPORT_SECTION -->
---
## 🔍 Automated QA Report

| | |
|---|---|
| **Status** | ✅ Complete |
| **Report** |
[sno-qa-10336.comfy-qa.pages.dev](https://sno-qa-10336.comfy-qa.pages.dev/)
|
| **CI Run** | [View
workflow](https://github.com/Comfy-Org/ComfyUI_frontend/actions/runs/23373697656)
|

Before/after video recordings with **Behavior Changes** and **Timeline
Comparison** tables.

browser_tests/tests/interaction.spec.ts

@@ -764,13 +764,13 @@ test.describe('Load workflow', { tag: '@screenshot' }, () => {
     )
   })
 
+  const generateUniqueFilename = (extension = '') =>
+    `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 8)}${extension}`
+
   test.describe('Restore all open workflows on reload', () => {
     let workflowA: string
     let workflowB: string
 
-    const generateUniqueFilename = (extension = '') =>
-      `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 8)}${extension}`
-
     test.beforeEach(async ({ comfyPage }) => {
       await comfyPage.settings.setSetting('Comfy.UseNewMenu', 'Top')
 
@@ -829,6 +829,82 @@ test.describe('Load workflow', { tag: '@screenshot' }, () => {
     })
   })
 
+  test.describe('Restore workflow tabs after browser restart', () => {
+    let workflowA: string
+    let workflowB: string
+
+    test.beforeEach(async ({ comfyPage }) => {
+      await comfyPage.settings.setSetting('Comfy.UseNewMenu', 'Top')
+
+      workflowA = generateUniqueFilename()
+      await comfyPage.menu.topbar.saveWorkflow(workflowA)
+      workflowB = generateUniqueFilename()
+      await comfyPage.menu.topbar.triggerTopbarCommand(['New'])
+      await comfyPage.menu.topbar.saveWorkflow(workflowB)
+
+      // Wait for localStorage fallback pointers to be written
+      await comfyPage.page.waitForFunction(() => {
+        for (let i = 0; i < window.localStorage.length; i++) {
+          const key = window.localStorage.key(i)
+          if (key?.startsWith('Comfy.Workflow.LastOpenPaths:')) {
+            return true
+          }
+        }
+        return false
+      })
+
+      // Simulate browser restart: clear sessionStorage (lost on close)
+      // but keep localStorage (survives browser restart)
+      await comfyPage.page.evaluate(() => {
+        sessionStorage.clear()
+      })
+      await comfyPage.setup({ clearStorage: false })
+    })
+
+    test('Restores topbar workflow tabs after browser restart', async ({
+      comfyPage
+    }) => {
+      await comfyPage.settings.setSetting(
+        'Comfy.Workflow.WorkflowTabsPosition',
+        'Topbar'
+      )
+      // Wait for both restored tabs to render (localStorage fallback is async)
+      await expect(
+        comfyPage.page.locator('.workflow-tabs .workflow-label', {
+          hasText: workflowA
+        })
+      ).toBeVisible()
+
+      const tabs = await comfyPage.menu.topbar.getTabNames()
+      const activeWorkflowName = await comfyPage.menu.topbar.getActiveTabName()
+
+      expect(tabs).toEqual(expect.arrayContaining([workflowA, workflowB]))
+      expect(tabs.indexOf(workflowA)).toBeLessThan(tabs.indexOf(workflowB))
+      expect(activeWorkflowName).toEqual(workflowB)
+    })
+
+    test('Restores sidebar workflows after browser restart', async ({
+      comfyPage
+    }) => {
+      await comfyPage.settings.setSetting(
+        'Comfy.Workflow.WorkflowTabsPosition',
+        'Sidebar'
+      )
+      await comfyPage.menu.workflowsTab.open()
+      const openWorkflows =
+        await comfyPage.menu.workflowsTab.getOpenedWorkflowNames()
+      const activeWorkflowName =
+        await comfyPage.menu.workflowsTab.getActiveWorkflowName()
+      expect(openWorkflows).toEqual(
+        expect.arrayContaining([workflowA, workflowB])
+      )
+      expect(openWorkflows.indexOf(workflowA)).toBeLessThan(
+        openWorkflows.indexOf(workflowB)
+      )
+      expect(activeWorkflowName).toEqual(workflowB)
+    })
+  })
+
   test('Auto fit view after loading workflow', async ({ comfyPage }) => {
     await comfyPage.settings.setSetting(
       'Comfy.EnableWorkflowViewRestore',