test: update E2E to expect missing nodes overlay on tab switch (#10190)

## Summary

- Update the E2E test expectation for missing nodes overlay behavior
when switching between opened workflows
- `showMissingNodes` was intentionally changed to `true` in
`workflowService.ts` so users always see missing node pack info when
switching tabs, allowing them to install missing packs without a page
reload
- The test previously asserted the overlay should NOT reappear; now it
asserts the overlay SHOULD reappear

## Test plan

- [x] CI E2E tests pass with updated expectation

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10190-test-update-E2E-to-expect-missing-nodes-overlay-on-tab-switch-3266d73d36508106a48efff7309bd4e5)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

browser_tests/tests/sidebar/workflows.spec.ts

@@ -232,7 +232,7 @@ test.describe('Workflows sidebar', () => {
       .toEqual('workflow1')
   })
 
-  test('Does not report warning when switching between opened workflows', async ({
+  test('Reports missing nodes warning again when switching back to workflow', async ({
     comfyPage
   }) => {
     await comfyPage.settings.setSetting(
@@ -254,10 +254,11 @@ test.describe('Workflows sidebar', () => {
     await comfyPage.menu.workflowsTab.open()
     await comfyPage.command.executeCommand('Comfy.NewBlankWorkflow')
 
-    // Switch back to the missing_nodes workflow — overlay should not reappear
+    // Switch back to the missing_nodes workflow — overlay should reappear
+    // so users can install missing node packs without a page reload
     await comfyPage.menu.workflowsTab.switchToWorkflow('missing_nodes')
 
-    await expect(errorOverlay).not.toBeVisible()
+    await expect(errorOverlay).toBeVisible()
   })
 
   test('Can close saved-workflows from the open workflows section', async ({