Function iqsm_plus 

pub fn iqsm_plus(
    phase_rad: &[f64],
    mask: &[u8],
    grid: &Grid,
    te: f64,
    b0: f64,
    b0_dir: (f64, f64, f64),
    phase_sign: f64,
    eroded_rad: i32,
    model_onnx: &[u8],
) -> Result<Vec<f64>, OnnxError>

Run iQSM+ on a single echo of wrapped phase.

• phase_rad, mask — column-major (nx,ny,nz).
• te (s), b0 (T), b0_dir — acquisition parameters (b0_dir normalized internally).
• phase_sign (-1 default), eroded_rad (3 default).

Returns susceptibility (ppm), masked, in the same layout.