feat: show loading spinner and uploading filename during image upload (#9189)

## Summary
- Show a canvas-based loading spinner on image upload nodes (LoadImage)
during file upload via drag-drop, paste, or file picker
- Display the uploading file's name immediately in the filename dropdown
instead of showing the previous file's name
- Show the uploading audio file's name immediately in the audio widget
during upload

## Changes
- **`useNodeImageUpload.ts`**: Add `isUploading` flag and
`onUploadStart` callback to the upload lifecycle; clear `node.imgs`
during upload to prevent stale previews
- **`useImagePreviewWidget.ts`**: Add `renderUploadSpinner` that draws
an animated arc spinner on the canvas when `node.isUploading` is true;
guard against empty `imgs` array
- **`useImageUploadWidget.ts`**: Set `fileComboWidget.value` to the new
filename on upload start; clear `node.imgs` on combo widget change
- **`uploadAudio.ts`**: Set `audioWidget.value` to the new filename on
upload start
- **`litegraph-augmentation.d.ts`**: Add `isUploading` property to
`LGraphNode`



https://github.com/user-attachments/assets/818ce529-cb83-428a-8c98-dd900a128343



## Test plan
- [x] Upload an image via file picker on LoadImage node — spinner shows
during upload, filename updates immediately
- [x] Drag-and-drop an image onto LoadImage node — same behavior
- [x] Paste an image onto LoadImage node — same behavior
- [x] Change the dropdown selection on LoadImage — old preview clears,
new image loads
- [x] Upload an audio file — filename updates immediately in the widget

🤖 Generated with [Claude Code](https://claude.com/claude-code)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9189-feat-show-loading-spinner-and-uploading-filename-during-image-upload-3126d73d365081e4af27cd7252f34298)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/renderer/extensions/vueNodes/widgets/composables/useImageUploadWidget.ts

@@ -54,12 +54,27 @@ export const useImageUploadWidget = () => {
       createAnnotatedPath(value, { rootFolder: image_folder })
 
     // Setup file upload handling
+    let rollback: (() => void) | undefined
     const { openFileSelection } = useNodeImageUpload(node, {
       allow_batch,
       fileFilter,
       accept,
       folder,
+      onUploadStart: (files) => {
+        if (files.length > 0) {
+          const prev = fileComboWidget.value
+          fileComboWidget.value = files[0].name
+          rollback = () => {
+            fileComboWidget.value = prev
+          }
+        }
+      },
+      onUploadError: () => {
+        rollback?.()
+        rollback = undefined
+      },
       onUploadComplete: (output) => {
+        rollback = undefined
         const annotated = output.map(formatPath)
         annotated.forEach((path) => {
           addToComboValues(fileComboWidget, path)
@@ -88,6 +103,7 @@ export const useImageUploadWidget = () => {
 
     // Add our own callback to the combo widget to render an image when it changes
     fileComboWidget.callback = function () {
+      node.imgs = undefined
       nodeOutputStore.setNodeOutputs(node, String(fileComboWidget.value), {
         isAnimated
       })