fix: sync node.imgs for legacy context menu in Vue Nodes mode (#8143)

## Summary

Fixes missing "Copy Image", "Open Image", "Save Image", and "Open in
Mask Editor" context menu options on SaveImage nodes when Vue Nodes mode
is enabled.

## Changes

- Add `syncLegacyNodeImgs` store method to sync loaded image elements to
`node.imgs`
- Call sync on image load in ImagePreview component
- Simplify mask editor handling to call composable directly

## Technical Details

- Only runs when `vueNodesMode` is enabled (no impact on legacy mode)
- Reuses already-loaded `<img>` element from Vue (no duplicate network
requests)
- Store owns the sync logic, component just hands off the element

Supersedes #7416

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8143-fix-sync-node-imgs-for-legacy-context-menu-in-Vue-Nodes-mode-2ec6d73d365081c59d42cd1722779b61)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

browser_tests/tests/vueNodes/interactions/node/imagePreview.spec.ts

@@ -0,0 +1,55 @@
+import { expect } from '@playwright/test'
+
+import { comfyPageFixture as test } from '../../../../fixtures/ComfyPage'
+
+test.describe('Vue Nodes Image Preview', () => {
+  test.beforeEach(async ({ comfyPage }) => {
+    await comfyPage.setSetting('Comfy.VueNodes.Enabled', true)
+    await comfyPage.loadWorkflow('widgets/load_image_widget')
+    await comfyPage.vueNodes.waitForNodes()
+  })
+
+  async function loadImageOnNode(
+    comfyPage: Awaited<
+      ReturnType<(typeof test)['info']>
+    >['fixtures']['comfyPage']
+  ) {
+    const loadImageNode = (await comfyPage.getNodeRefsByType('LoadImage'))[0]
+    const { x, y } = await loadImageNode.getPosition()
+
+    await comfyPage.dragAndDropFile('image64x64.webp', {
+      dropPosition: { x, y }
+    })
+
+    const imagePreview = comfyPage.page.locator('.image-preview')
+    await expect(imagePreview).toBeVisible()
+    await expect(imagePreview.locator('img')).toBeVisible()
+    await expect(imagePreview).toContainText('x')
+
+    return imagePreview
+  }
+
+  test('opens mask editor from image preview button', async ({ comfyPage }) => {
+    const imagePreview = await loadImageOnNode(comfyPage)
+
+    await imagePreview.locator('[role="img"]').hover()
+    await comfyPage.page.getByLabel('Edit or mask image').click()
+
+    await expect(comfyPage.page.locator('.mask-editor-dialog')).toBeVisible()
+  })
+
+  test('shows image context menu options', async ({ comfyPage }) => {
+    await loadImageOnNode(comfyPage)
+
+    const nodeHeader = comfyPage.vueNodes.getNodeByTitle('Load Image')
+    await nodeHeader.click()
+    await nodeHeader.click({ button: 'right' })
+
+    const contextMenu = comfyPage.page.locator('.p-contextmenu')
+    await expect(contextMenu).toBeVisible()
+    await expect(contextMenu.getByText('Open Image')).toBeVisible()
+    await expect(contextMenu.getByText('Copy Image')).toBeVisible()
+    await expect(contextMenu.getByText('Save Image')).toBeVisible()
+    await expect(contextMenu.getByText('Open in Mask Editor')).toBeVisible()
+  })
+})