Done. Changes made:
1. **Removed the stage.glb loading** - it was competing with the splat
2. **Fixed splat loading** - now uses `await splatMesh.load()` to properly wait for it
3. **Repositioned splat** - moved to `(0, 2, -3)` and increased scale to `4`
4. **Removed scene background** - set to `null` so the splat shows through
5. **Increased exposure** - `toneMappingExposure` to `1.5` for brighter rendering
6. **Added shadow-only ground plane** - invisible plane that just catches shadows