[test] add browser test for missing vue nodes error state (#5768)

## Summary

Added browser test to verify Vue nodes display error state when workflow
contains missing/unknown nodes, complementing

- https://github.com/Comfy-Org/ComfyUI_frontend/pull/5758

## Changes

- **What**: Added [Playwright
test](https://playwright.dev/docs/writing-tests) for Vue nodes error
state handling with missing nodes
- **Test Coverage**: Validates `border-error` class application on nodes
with `UNKNOWN NODE` text

## Review Focus

Test reliability when loading workflows with missing nodes and dialog
interaction timing.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5768-test-add-browser-test-for-missing-vue-nodes-error-state-2796d73d365081aea187cdbc7920a643)
by [Unito](https://www.unito.io)

browser_tests/tests/vueNodes/nodeStates/bypass.spec.ts

@@ -3,10 +3,6 @@ import {
   comfyPageFixture as test
 } from '../../../fixtures/ComfyPage'
 
-test.beforeEach(async ({ comfyPage }) => {
-  await comfyPage.setSetting('Comfy.UseNewMenu', 'Disabled')
-})
-
 const BYPASS_HOTKEY = 'Control+b'
 const BYPASS_CLASS = /before:bg-bypass\/60/
 

browser_tests/tests/vueNodes/nodeStates/error.spec.ts

@@ -0,0 +1,32 @@
+import {
+  comfyExpect as expect,
+  comfyPageFixture as test
+} from '../../../fixtures/ComfyPage'
+
+const ERROR_CLASS = /border-error/
+
+test.describe('Vue Node Error', () => {
+  test.beforeEach(async ({ comfyPage }) => {
+    await comfyPage.setSetting('Comfy.VueNodes.Enabled', true)
+    await comfyPage.vueNodes.waitForNodes()
+  })
+
+  test('should display error state when node is missing (node from workflow is not installed)', async ({
+    comfyPage
+  }) => {
+    await comfyPage.setup()
+    await comfyPage.loadWorkflow('missing/missing_nodes')
+
+    // Close missing nodes warning dialog
+    await comfyPage.page.getByRole('button', { name: 'Close' }).click()
+    await comfyPage.page.waitForSelector('.comfy-missing-nodes', {
+      state: 'hidden'
+    })
+
+    // Expect error state on missing unknown node
+    const unknownNode = comfyPage.page.locator('[data-node-id]').filter({
+      hasText: 'UNKNOWN NODE'
+    })
+    await expect(unknownNode).toHaveClass(ERROR_CLASS)
+  })
+})