fix: initialize cameraFov observer to match actual camera FOV in LOD streaming example (#8510)

The FOV slider defaulted to its minimum (10) because the cameraFov observer
value was never set, while the camera was created with fov: 75.

Made-with: Cursor

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>

Author: mvaligursky

examples/src/examples/gaussian-splatting/lod-streaming.example.mjs

@@ -149,6 +149,7 @@ assetListLoader.load(() => {
     });
 
     // initialize UI settings (must be after observer registration)
+    data.set('cameraFov', 75);
     data.set('gpuSorting', false);
     data.set('culling', device.isWebGPU);
     data.set('compact', true);