Fix: Widget sizing with multiple expanding items (#7118)

## Summary

Textarea/Markdown/3D pieces grow, other widget rows size to their
contents.

## Screenshots (if applicable)
<img width="564" height="420" alt="image"
src="https://github.com/user-attachments/assets/35aeb9bf-a44d-4e3f-b2cd-a9f3604a7778"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7118-Fix-Widget-sizing-with-multiple-expanding-items-2be6d73d3650816c8153ff3f1e49176d)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Simula_r <18093452+simula-r@users.noreply.github.com>
Co-authored-by: github-actions <github-actions@github.com>

src/components/load3d/Load3D.vue

@@ -1,6 +1,6 @@
 <template>
   <div
-    class="widget-expands relative h-full w-full"
+    class="relative size-full"
     @mouseenter="handleMouseEnter"
     @mouseleave="handleMouseLeave"
     @pointerdown.stop
@@ -17,7 +17,7 @@
       :on-model-drop="isPreview ? undefined : handleModelDrop"
       :is-preview="isPreview"
     />
-    <div class="pointer-events-none absolute top-0 left-0 h-full w-full">
+    <div class="pointer-events-none absolute top-0 left-0 size-full">
       <Load3DControls
         v-model:scene-config="sceneConfig"
         v-model:model-config="modelConfig"