Function run_nextqsm 

pub fn run_nextqsm(
    total_field_ppm: &[f64],
    mask: &[u8],
    grid: &Grid,
    bdir: (f64, f64, f64),
    tile: Option<(usize, usize)>,
    progress: &mut dyn FnMut(usize, usize),
) -> Result<Vec<f64>, PipelineError>

Run NeXtQSM end-to-end from the total field (it does its own background removal), sourcing both weight files from the registry. Unlike the entries in InversionAlgorithm, NeXtQSM spans BFR + dipole inversion, so it is exposed as a standalone reconstruction rather than a dipole-inversion-stage option.

total_field_ppm and mask are column-major (nx,ny,nz); bdir is the B0 direction. Requires the onnx feature; weights resolve local-first then via the download feature. Returns susceptibility (ppm), masked.