OVRTX render settings

Run ovrtx-addon-install-and-preflight, then use ovrtx-current-scene-workflow/scripts/probe_ovrtx_scene.py to inspect the installed surface. The tested public add-on registers engine OVRTX_EXAMPLE and Scene.ovrtx_example; probe rather than assuming versioned fields.

Use scripts/configure_scene_settings.py in a bounded Blender process or append its source to a blender-python-execution MCP call with OVRTX_SETTINGS_REQUEST. The helper validates enum/range/order constraints and restores all touched fields if any mutation fails.