Function minimum_angle_optimization 

pub fn minimum_angle_optimization(
    positions: &mut [[f64; 3]],
    triangles: &[[usize; 3]],
    iterations: usize,
) -> usize

Apply angle-based smoothing to a 2-D triangle mesh.

Moves each interior vertex to maximise the minimum interior angle in surrounding triangles. Uses a gradient-free search along the Laplacian direction with a line search.

Returns the number of accepted vertex moves.