608e6135

By: ValentinHirschi <valentin.hirschi@gmail.com>

fix hyperspherical angular jacobians

Use D-3-i for the uniform-cosine angular factors in both the forward
parameterization and its inverse. Check the actual Cartesian determinant
independently, including D12 with higher_loops and three radial mappings.

Validation: cargo fmt --all --check; locked gammalooprs check and Clippy
with higher_loops; six focused nextest parameterization tests passed.

User prompt:
Yeah I don't exactly remember what these two modes `relative_spherical` and `spherical_product_common_radial`, i think it's just normal spherical cartesian produce but with another overall hyperradius scaling, but I don't think it's useful to you anyway.
And yes please push your fix in the hyperspherical jacobian if you're sure about it too.

So what kind of sampling is needed to tame that remaining integrable singularity in GL638? And is arb prec not enough for your stability issues in GL638; can you explain the issue better there?