Feat/3d dropdown (#8765)

## Summary
Add mesh_upload and upload_subfolder to combo input schema so
WidgetSelect detects mesh uploads generically instead of hardcoding node
type checks. Inject these flags in load3dLazy.ts so they are available
before THREE.js loads.

Also unify SUPPORTED_EXTENSIONS_ACCEPT across load3d and dropdown, pass
uploadSubfolder prop through to WidgetSelectDropdown for correct upload
path, and update error message to list all supported extensions.

replacement for https://github.com/Comfy-Org/ComfyUI_frontend/pull/7975

(We should include thumbnail but not yet, will do it later)

## Screenshots (if applicable)


https://github.com/user-attachments/assets/2cb4b1da-af4f-439b-9786-3ac780c2480d

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8765-Feat-3d-dropdown-3036d73d365081d8a10ee19d3ed7d295)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Kelly Yang <124ykl@gmail.com>

src/extensions/core/load3d.ts

@@ -9,6 +9,7 @@ import type {
   CameraState
 } from '@/extensions/core/load3d/interfaces'
 import Load3DConfiguration from '@/extensions/core/load3d/Load3DConfiguration'
+import { SUPPORTED_EXTENSIONS_ACCEPT } from '@/extensions/core/load3d/constants'
 import Load3dUtils from '@/extensions/core/load3d/Load3dUtils'
 import { t } from '@/i18n'
 import type { LGraphNode } from '@/lib/litegraph/src/LGraphNode'
@@ -258,10 +259,7 @@ useExtensionService().registerExtension({
   getCustomWidgets() {
     return {
       LOAD_3D(node) {
-        const fileInput = createFileInput(
-          '.gltf,.glb,.obj,.fbx,.stl,.ply,.spz,.splat,.ksplat',
-          false
-        )
+        const fileInput = createFileInput(SUPPORTED_EXTENSIONS_ACCEPT, false)
 
         node.properties['Resource Folder'] = ''
 

src/extensions/core/load3d/constants.ts

@@ -14,3 +14,5 @@ export const SUPPORTED_EXTENSIONS = new Set([
   '.ply',
   '.ksplat'
 ])
+
+export const SUPPORTED_EXTENSIONS_ACCEPT = [...SUPPORTED_EXTENSIONS].join(',')

src/extensions/core/load3dLazy.ts

@@ -56,6 +56,16 @@ useExtensionService().registerExtension({
 
   async beforeRegisterNodeDef(nodeType, nodeData) {
     if (isLoad3dNodeType(nodeData.name)) {
+      // Inject mesh_upload spec flags so WidgetSelect.vue can detect
+      // Load3D's model_file as a mesh upload widget without hardcoding.
+      if (nodeData.name === 'Load3D') {
+        const modelFile = nodeData.input?.required?.model_file
+        if (modelFile?.[1]) {
+          modelFile[1].mesh_upload = true
+          modelFile[1].upload_subfolder = '3d'
+        }
+      }
+
       // Load the 3D extensions and replay their beforeRegisterNodeDef hooks,
       // since invokeExtensionsAsync already captured the extensions snapshot
       // before these new extensions were registered.