- IVROverlayView reads system overlays (systemui, HeadsetView) but not
Steam's dmabuf-backed panels
- SteamVR systemui scene graph accepts injected nodes (DOM elements with
buildNode; submit via module 5723's scheduler): reparent-to-panel +
panel-anchor + transform + panel shows live crops of Steam's window at
any 3D offset, and our own dmabuf overlays (needs SetOverlayMouseScale)
- hvgrab: headset-view capture for verification
