Fix Ruff lint failures

[timkpaine]

Description

Update Python syntax selected by current Ruff, use TypeError for invalid validator input types, and make split-string concatenation explicit. 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

63 tests  ±0   63 ✅ ±0   16s ⏱️ -1s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 06d9c06. ± Comparison against base commit fe956cf.

[codecov]

Codecov Report

❌ Patch coverage is 97.75281% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.42%. Comparing base (fe956cf) to head (06d9c06).

Files with missing lines	Patch %	Lines
hatch_rs/structs.py	97.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #68      +/-   ##
==========================================
+ Coverage   81.40%   81.42%   +0.02%     
==========================================
  Files          10       10              
  Lines        1441     1443       +2     
==========================================
+ Hits         1173     1175       +2     
  Misses        268      268              

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