chore: Add Python 3.14 tests

[effigies]

Not all of our dependencies can be installed on 3.14 just yet, so leaving this as a draft.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.37%. Comparing base (587f74c) to head (c8d6f62).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1175   +/-   ##
=======================================
  Coverage   89.37%   89.37%           
=======================================
  Files          66       66           
  Lines        7276     7276           
  Branches      854      854           
=======================================
  Hits         6503     6503           
  Misses        565      565           
  Partials      208      208           

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