fix: allow URI drops to bubble from Vue nodes to document handler (#9463)

## Summary

Fix URI drops (e.g. dragging `<img>` thumbnails) onto Vue-rendered nodes
by letting unhandled drops bubble to the document-level `text/uri-list`
fallback in `app.ts`.

## Changes

- **What**: Removed unconditional `.stop` modifier from `@drop` in
`LGraphNode.vue`. `stopPropagation()` is now called conditionally — only
when `onDragDrop` returns `true` (file drop handled). Made `handleDrop`
synchronous since `onDragDrop` returns a plain boolean.

## Review Focus

The key insight is that `onDragDrop` (from `useNodeDragAndDrop`) returns
`false` synchronously for URI drags (no files in `DataTransfer`), so the
event must bubble to reach the document handler that fetches the URI.
The original `async` + `await` pattern would have deferred
`stopPropagation` past the synchronous propagation phase, so
`handleDrop` is now synchronous.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9463-fix-allow-URI-drops-to-bubble-from-Vue-nodes-to-document-handler-31b6d73d36508196a1b3f17e7e4837a9)
by [Unito](https://www.unito.io)

browser_tests/fixtures/helpers/DragDropHelper.ts

@@ -25,13 +25,15 @@ export class DragDropHelper {
       url?: string
       dropPosition?: Position
       waitForUpload?: boolean
+      preserveNativePropagation?: boolean
     } = {}
   ): Promise<void> {
     const {
       dropPosition = { x: 100, y: 100 },
       fileName,
       url,
-      waitForUpload = false
+      waitForUpload = false,
+      preserveNativePropagation = false
     } = options
 
     if (!fileName && !url)
@@ -43,7 +45,8 @@ export class DragDropHelper {
       fileType?: string
       buffer?: Uint8Array | number[]
       url?: string
-    } = { dropPosition }
+      preserveNativePropagation: boolean
+    } = { dropPosition, preserveNativePropagation }
 
     if (fileName) {
       const filePath = this.assetPath(fileName)
@@ -115,15 +118,17 @@ export class DragDropHelper {
         )
       }
 
-      Object.defineProperty(dropEvent, 'preventDefault', {
-        value: () => {},
-        writable: false
-      })
+      if (!params.preserveNativePropagation) {
+        Object.defineProperty(dropEvent, 'preventDefault', {
+          value: () => {},
+          writable: false
+        })
 
-      Object.defineProperty(dropEvent, 'stopPropagation', {
-        value: () => {},
-        writable: false
-      })
+        Object.defineProperty(dropEvent, 'stopPropagation', {
+          value: () => {},
+          writable: false
+        })
+      }
 
       targetElement.dispatchEvent(dragOverEvent)
       targetElement.dispatchEvent(dropEvent)
@@ -154,7 +159,10 @@ export class DragDropHelper {
 
   async dragAndDropURL(
     url: string,
-    options: { dropPosition?: Position } = {}
+    options: {
+      dropPosition?: Position
+      preserveNativePropagation?: boolean
+    } = {}
   ): Promise<void> {
     return this.dragAndDropExternalResource({ url, ...options })
   }