Introduce Python 3.14 compatibility

[whitequark]

The new annotationlib module is required reading for understanding this PR, as well as the relevant PEPs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.28%. Comparing base (1b62e0c) to head (f265b89).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1634      +/-   ##
==========================================
+ Coverage   91.26%   91.28%   +0.02%     
==========================================
  Files          44       44              
  Lines       11444    11471      +27     
  Branches     2230     2236       +6     
==========================================
+ Hits        10444    10471      +27     
  Misses        837      837              
  Partials      163      163              

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