[MNT] CI: Add Python 3.14 to test matrix

[ales-erjavec]

Issue

Add Python 3.14 to test matrix

Also fix silently failing test on windows

Description of changes

Includes

• Code changes
• Tests
• Documentation

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.04%. Comparing base (9fcf2ab) to head (2c5003a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #286      +/-   ##
==========================================
- Coverage   72.04%   72.04%   -0.01%     
==========================================
  Files          34       34              
  Lines        9116     9115       -1     
==========================================
- Hits         6568     6567       -1     
  Misses       2548     2548              

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