[test] add browser tests for Vue node multiline string widgets (#5819)

## Summary

Added Playwright E2E tests for Vue multiline string widget functionality
to ensure text input and persistence work correctly.

## Changes

- **What**: Created browser tests for multiline string widget in Vue
nodes implementation, covering text input, multiline text input, and
focus change behavior.

## Review Focus

Test coverage for text input persistence across focus changes and
multiline content handling in the CLIP Text Encode widget.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5819-test-add-browser-tests-for-Vue-node-multiline-string-widgets-27b6d73d365081e2916ae663e2d44899)
by [Unito](https://www.unito.io)

browser_tests/tests/vueNodes/widgets/text/multilineStringWidget.spec.ts

@@ -0,0 +1,49 @@
+import {
+  type ComfyPage,
+  comfyExpect as expect,
+  comfyPageFixture as test
+} from '../../../../fixtures/ComfyPage'
+
+test.describe('Vue Multiline String Widget', () => {
+  test.beforeEach(async ({ comfyPage }) => {
+    await comfyPage.setSetting('Comfy.VueNodes.Enabled', true)
+    await comfyPage.vueNodes.waitForNodes()
+  })
+
+  const getFirstClipNode = (comfyPage: ComfyPage) =>
+    comfyPage.vueNodes.getNodeByTitle('CLIP Text Encode (Prompt)').first()
+
+  const getFirstMultilineStringWidget = (comfyPage: ComfyPage) =>
+    getFirstClipNode(comfyPage).getByRole('textbox', { name: 'text' })
+
+  test('should allow entering text', async ({ comfyPage }) => {
+    const textarea = getFirstMultilineStringWidget(comfyPage)
+    await textarea.fill('Hello World')
+    await expect(textarea).toHaveValue('Hello World')
+    await textarea.fill('Hello World 2')
+    await expect(textarea).toHaveValue('Hello World 2')
+  })
+
+  test('should support entering multiline content', async ({ comfyPage }) => {
+    const textarea = getFirstMultilineStringWidget(comfyPage)
+
+    const multilineValue = ['Line 1', 'Line 2', 'Line 3'].join('\n')
+
+    await textarea.fill(multilineValue)
+    await expect(textarea).toHaveValue(multilineValue)
+  })
+
+  test('should retain value after focus changes', async ({ comfyPage }) => {
+    const textarea = getFirstMultilineStringWidget(comfyPage)
+
+    await textarea.fill('Keep me around')
+
+    // Click another node
+    const loadCheckpointNode =
+      comfyPage.vueNodes.getNodeByTitle('Load Checkpoint')
+    await loadCheckpointNode.click()
+    await getFirstClipNode(comfyPage).click()
+
+    await expect(textarea).toHaveValue('Keep me around')
+  })
+})