Describe the bug
The mac startup is throwing an error at multiprocessing.set_start_method('spawn')

To Reproduce
Steps to reproduce the behavior:

1. cd to the sasview source directory
2. type python run.py

Expected behavior
Rebuild GUI and start sasview in the context of the local versions of sasmodels, sasdata, bumps, periodictable

Screenshots

$ python run.py             
Traceback (most recent call last):
  File "/Users/pkienzle/Source/sasview/run.py", line 90, in <module>
    multiprocessing.set_start_method('spawn')
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/Users/pkienzle/.local/share/uv/python/cpython-3.13.5-macos-aarch64-none/lib/python3.13/multiprocessing/context.py", line 247, in set_start_method
    raise RuntimeError('context has already been set')
RuntimeError: context has already been set

SasView version (please complete the following information):

• Version: 5fa6925

Operating system (please complete the following information):

• OS: OS X Sequoia 15.6.1

Installation method (please complete the following information):

• Installed: git clone

Additional context
Commenting out the line in run.py works for Mac and makes the Windows startup faster.