mlx - numpy fix scalar handling and skip float 64 tests

[lkarthee]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 38 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (mlx@ba0c886). Click here to learn what that means.

Files	Patch %	Lines
keras/src/backend/mlx/numpy.py	0.00%	38 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##             mlx   #19613   +/-   ##
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  Coverage       ?   68.48%           
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  Files          ?      506           
  Lines          ?    45935           
  Branches       ?     8496           
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  Hits           ?    31457           
  Misses         ?    12829           
  Partials       ?     1649           

Flag	Coverage Δ
keras	68.40% <0.00%> (?)
keras-jax	58.87% <0.00%> (?)
keras-numpy	53.19% <0.00%> (?)
keras-tensorflow	60.00% <0.00%> (?)

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[fchollet]

LGTM, thanks!