Function tikhonov_default 

pub fn tikhonov_default(
    local_field: &[f64],
    mask: &[u8],
    nx: usize,
    ny: usize,
    nz: usize,
    vsx: f64,
    vsy: f64,
    vsz: f64,
) -> Vec<f64>

Tikhonov with default parameters (identity regularization, λ=0.01; matches QSM.jl)