Fix some gallery files not being executed

[echedey-ls]

• Closes Missing thumbnails in the example gallery #2790
• I am familiar with the contributing guidelines
• I attest that there is no AI-generated material in this PR, just like the good old days
• Tests added
• Updates entries in docs/sphinx/source/reference for API changes.
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels (including remote-data) and Milestone are assigned to the Pull Request and linked Issue.

Other suggestions for the prefix welcome. I left a warning in NX_oedi9068.py to explicitly state it is not run by documentation. I don't really care but I thought it may be useful to hint users before running.

[echedey-ls]

regex ^(?!.*/)*((?!/NX_).)*$ was tested with the following test batch:

# True negatives
/NX_test1.py
/NX_oedi.py
/NX_.rst
/NX_.py
/NX__.py
/home/echedey/Documents/10_Programming/pvlib-python/docs/examples/system-models/NX_oedi_9068.py
# These are considered negatives; I differ a little bit but I don't know how feasible is to make the regex match so
/NX_/hello.py
/NX_what/hello.py
# True positives
/index.rst
/plot_test1.py
/plot_oedi.py
/oedi.py
/__lalilailola__.py
/white spaces.py
/special chars?.py
/is_middle_NX_detected.py
/home/echedey/Documents/10_Programming/pvlib-python/docs/examples/system-models/oedi_9068.py

https://regex101.com/ - remember to change to python flavor if you try it.

Edit: updated regex and test data at 00h30 UTC 2026-06-19

Last edit: I invite anybody on windows to try this out, I only checked on linux which is enough for the readthedocs builds, but you may want to check windows users can use this locally too.