- Fix all clippy lint warnings across codebase
- Update CHANGELOG.md with v0.2.1 release notes
- Bump version from 0.2.0 to 0.2.1

Changes include:
- Fix cast_sign_loss in dataset modules
- Fix manual_range_contains patterns
- Fix uninlined_format_args in examples and tests
- Fix needless_pass_by_value in doctest parser
- Fix unused imports and variables
- Add allow attributes for test-only code

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>