[abc] argshift: fix erroneous L2 norm.

modifying _Stencil_CP for compatibility with numpy>=2

[ex] Update tomo example to Pyxu v2.

[doc] Minor typo fix.

[SWE] Bump Dask/Numpy/Zarr max-ver.

[doc][refactor] sphinx-gallery update requires GALLERY_HEADER.rst... (3)

Remove nufft classes.

Have been moved to pyxu_nufft/ repo.

[SWE] Update working notes.

[xrt] Add updated Lipschitz estimates.

[SWE] Use seperate target for GUI dependencies.

These are useful when installing Pyxu in user environments such as
Jupyter notebooks. We refactor them out to not have to pull all dev
dependencies to use them.