Gap-free room scan execution
The intended test flow is: capture on the LiDAR iPhone app, tap Upload scan, keep the vision service running on your Mac, then refresh this route and open the real scan id that was just uploaded. The demo path exists only to exercise the viewer shell when no device-backed scan is available.
Supported walkthrough volume
No real viewer package loaded yet
Upload a scan from the iPhone app, or seed the explicit demo if you only want to test the web viewer shell.