Ruff: Stricter code quality rules

[tony]

Docs:

• https://beta.ruff.rs/docs/rules/
• https://beta.ruff.rs/docs/settings/

See also: cihai/cihai#353, cihai/unihan-etl#290

[codecov]

Codecov Report

Merging #295 (8eea2d5) into master (3460ea5) will decrease coverage by 0.19%.
The diff coverage is 91.66%.

@@            Coverage Diff             @@
##           master     #295      +/-   ##
==========================================
- Coverage   74.91%   74.72%   -0.19%     
==========================================
  Files           5        5              
  Lines         287      277      -10     
==========================================
- Hits          215      207       -8     
+ Misses         72       70       -2     

Impacted Files	Coverage Δ
docs/conf.py	59.40% <ø> (ø)
src/cihai_cli/cli.py	72.94% <75.00%> (-0.63%)	⬇️
tests/conftest.py	97.14% <100.00%> (-0.08%)	⬇️
tests/test_cli.py	88.63% <100.00%> (+2.36%)	⬆️

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