49211a05c5
This change allows users to provide an optional `step_fn` callable to `StudioApp.update` and `StudioApp.update_from_viewer`. When provided, this function is called to advance the physics simulation instead of the default `step_control.advance`. PiperOrigin-RevId: 925439890 Change-Id: Ia833503f6dd0c22fb8d75af6c5f06757496853e5