fn unwrap_voxel(new: f64, old: f64) -> f64
Temporal unwrap: remove 2π wraps by comparing to a reference value.
Matches ROMEO.jl: unwrapvoxel(new, old) = new - 2π * round((new - old) / 2π)
unwrapvoxel(new, old) = new - 2π * round((new - old) / 2π)