deprecate Python 3.9

[bendichter]

EOL was Oct 31 2025

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.85%. Comparing base (293af8c) to head (e777f26).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2141      +/-   ##
==========================================
- Coverage   95.23%   94.85%   -0.39%     
==========================================
  Files          29       29              
  Lines        2876     2876              
  Branches      740      740              
==========================================
- Hits         2739     2728      -11     
- Misses         83       93      +10     
- Partials       54       55       +1     

Flag	Coverage Δ
integration	74.02% <ø> (-0.42%)	⬇️
unit	84.94% <ø> (ø)

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[stephprince]

One other suggestion otherwise looks good to me! I will let @rly add any comments and can then update the PR required checks to use the new minimum test workflow versions before merging.

[rly]

Thanks for this PR @bendichter ! It looks all good to me. This should be in a minor release. We should also explore adding Python 3.14 support in a separate PR.

[rly]

We'll make a bugfix release imminently and then do a minor release with this PR deprecating python 3.9 shortly after