Function cpu_pick_node_at 

pub fn cpu_pick_node_at(
    tensor: &[u8],
    canvas_w: f64,
    canvas_h: f64,
    pick_x: f64,
    pick_y: f64,
    yaw: f32,
    standpoint: &ObserverStandpoint,
) -> Option<u32>

Canvas2D fallback pick — nearest projected node within hit radius (px).