merge: resolve conflicts with main for on-demand extension loading

Resolve 47 merge conflicts from merging main into the on-demand
extension loading branch. Key decisions:

- Accept main's maskeditor cleanup (composables+stores architecture)
- Keep branch's glob+dispatch on-demand loading in core/index.ts
- Port main's new load3d features (constants, FastPLYLoader, Asset
  Browser button) into branch's extensions/ directory structure
- Combine main's async settings loading with branch's
  processExtensionSettings callback
- Inject on-demand widget loading into main's standalone functions
  in litegraphService.ts
- Fix import paths for files referencing old load3d/maskeditor paths
- Allow processExtensionSettings worker re-registration for test
  compatibility

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/load3d/controls/viewer/ViewerModelControls.vue

@@ -10,7 +10,7 @@
       />
     </div>
 
-    <div>
+    <div v-if="!hideMaterialMode">
       <label>{{ $t('load3d.materialMode') }}</label>
       <Select
         v-model="materialMode"
@@ -25,12 +25,18 @@
 <script setup lang="ts">
 import Select from 'primevue/select'
 import { computed } from 'vue'
+import { useI18n } from 'vue-i18n'
 
 import type {
   MaterialMode,
   UpDirection
 } from '@/extensions/core/extensions/load3d/interfaces'
-import { t } from '@/i18n'
+
+const { t } = useI18n()
+const { hideMaterialMode = false, isPlyModel = false } = defineProps<{
+  hideMaterialMode?: boolean
+  isPlyModel?: boolean
+}>()
 
 const upDirection = defineModel<UpDirection>('upDirection')
 const materialMode = defineModel<MaterialMode>('materialMode')
@@ -46,10 +52,22 @@ const upDirectionOptions = [
 ]
 
 const materialModeOptions = computed(() => {
-  return [
-    { label: t('load3d.materialModes.original'), value: 'original' },
+  const options = [
+    { label: t('load3d.materialModes.original'), value: 'original' }
+  ]
+
+  if (isPlyModel) {
+    options.push({
+      label: t('load3d.materialModes.pointCloud'),
+      value: 'pointCloud'
+    })
+  }
+
+  options.push(
     { label: t('load3d.materialModes.normal'), value: 'normal' },
     { label: t('load3d.materialModes.wireframe'), value: 'wireframe' }
-  ]
+  )
+
+  return options
 })
 </script>