Show node output images on Vue Nodes (#5456)

* add image outputs on Vue nodes

* add unit tests and update cursor pointer

* use testing pinia

* properly mock i18n in component test

* get node via current graph

* use subgraph ID from node creation

* add better error handling for downloadFile util

* refactor: simplify image preview component architecture

- Replace awkward composable pattern with standard Vue component state
- Fix reactivity issues where images didn't update on new outputs
- Add proper subgraph-aware node resolution using NodeLocatorId
- Enhance accessibility with keyboard navigation and ARIA labels
- Add comprehensive error handling and loading states
- Include PrimeVue Skeleton for better loading UX
- Remove unused composable and test files

The image preview now properly updates when new outputs are generated
and follows standard Vue reactivity patterns.

* resolve merge conflict with main

- Keep both subgraphId field and hasErrors field from main
- No conflicts in other files (LGraphNode.vue and main.json merged cleanly)

* Fix LGraphNode test by adding proper Pinia testing setup

Added createTestingPinia and i18n configuration following the pattern
from working ImagePreview tests. Resolves test failures due to missing
Pinia store dependencies. All 6 tests now pass successfully.

src/base/common/downloadUtil.ts

@@ -0,0 +1,41 @@
+/**
+ * Utility functions for downloading files
+ */
+
+// Constants
+const DEFAULT_DOWNLOAD_FILENAME = 'download.png'
+
+/**
+ * Download a file from a URL by creating a temporary anchor element
+ * @param url - The URL of the file to download (must be a valid URL string)
+ * @param filename - Optional filename override (will use URL filename or default if not provided)
+ * @throws {Error} If the URL is invalid or empty
+ */
+export const downloadFile = (url: string, filename?: string): void => {
+  if (!url || typeof url !== 'string' || url.trim().length === 0) {
+    throw new Error('Invalid URL provided for download')
+  }
+  const link = document.createElement('a')
+  link.href = url
+  link.download =
+    filename || extractFilenameFromUrl(url) || DEFAULT_DOWNLOAD_FILENAME
+
+  // Trigger download
+  document.body.appendChild(link)
+  link.click()
+  document.body.removeChild(link)
+}
+
+/**
+ * Extract filename from a URL's query parameters
+ * @param url - The URL to extract filename from
+ * @returns The extracted filename or null if not found
+ */
+const extractFilenameFromUrl = (url: string): string | null => {
+  try {
+    const urlObj = new URL(url, window.location.origin)
+    return urlObj.searchParams.get('filename')
+  } catch {
+    return null
+  }
+}