NumPy 2.1 compatibility for xarray interpolation

[yaugenst-flex]

Fix TypeError in Box.derivative_face when using NumPy 2.1+ by explicitly converting coord_normal_face from numpy.float64 to Python float before passing to xarray's interpolation. This addresses stricter type checking in NumPy 2.1 while maintaining the same numerical behavior.

Previously this would error like:

...
  File "/Users/yannick/flexcompute/worktrees/surfacemesh_interp/tidy3d/components/geometry/base.py", line 2466, in integrate_face
    arr_at_face = arr.interp(**{dim_normal: coord_normal_face}, assume_sorted=True)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yannick/flexcompute/worktrees/surfacemesh_interp/tidy3d/components/data/data_array.py", line 343, in interp
    return super().interp(coords, method, assume_sorted, kwargs, **coords_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yannick/flexcompute/worktrees/surfacemesh_interp/.venv/lib/python3.12/site-packages/xarray/core/dataarray.py", line 2341, in interp
    ds = self._to_temp_dataset().interp(
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yannick/flexcompute/worktrees/surfacemesh_interp/.venv/lib/python3.12/site-packages/xarray/core/dataset.py", line 4004, in interp
    indexers = dict(self._validate_interp_indexers(coords))
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yannick/flexcompute/worktrees/surfacemesh_interp/.venv/lib/python3.12/site-packages/xarray/core/dataset.py", line 2859, in _validate_interp_indexers
    raise TypeError(type(v))
TypeError: <class 'numpy.float64'>

[notion-workspace]

⁉️ interp erroring in DerivativeSurfaceMesh

[fyc2646]

Thanks @yaugenst-flex

[tomflexcompute]

Sorry for using the wrong github login 😅