load assets browser before fetch completes and show loading state (#6189)

## Summary

Moves the fetch and post-fetch logic associated with the asset browser
into the component and shows a loading state while fetching.

To test, use this branch:
https://github.com/comfyanonymous/ComfyUI/pull/10045



https://github.com/user-attachments/assets/718974d5-efc7-46a0-bcd6-e82596d4c389

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6189-load-assets-browser-before-fetch-completes-and-show-loading-state-2946d73d365081879d1bd05d86e8c036)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

src/platform/assets/utils/categoryLabel.ts

@@ -0,0 +1,16 @@
+const ACRONYM_TAGS = new Set(['VAE', 'CLIP', 'GLIGEN'])
+
+export function formatCategoryLabel(raw?: string): string {
+  if (!raw) return 'Models'
+
+  return raw
+    .split('_')
+    .map((segment) => {
+      const upper = segment.toUpperCase()
+      if (ACRONYM_TAGS.has(upper)) return upper
+
+      const lower = segment.toLowerCase()
+      return lower.charAt(0).toUpperCase() + lower.slice(1)
+    })
+    .join(' ')
+}