Preserve runtime typing under Ruff rules

[timkpaine]

Description

Preserve typing.Optional and typing.Union runtime objects through aliases so p2a continues to parse union-typed model fields while satisfying Ruff UP007 and UP045. Ruff configuration remains unchanged.

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / code cleanup
• CI / build configuration
• Other (describe below)

Checklist

• Linting passes (make lint)
• Tests pass (make test)
• New tests added for new functionality
• Documentation updated (if applicable)
• Changelog / version bump (if applicable)

[github-actions]

Test Results

9 tests   9 ✅  1s ⏱️
1 suites  0 💤
1 files    0 ❌

Results for commit ef6aa7d.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.47%. Comparing base (a426267) to head (ef6aa7d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
+ Coverage   96.44%   96.47%   +0.03%     
==========================================
  Files           5        5              
  Lines         225      227       +2     
  Branches        7        7              
==========================================
+ Hits          217      219       +2     
  Misses          7        7              
  Partials        1        1              

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