chore: merge main into chore/refactor-2015

Resolved conflicts by keeping refactored versions:
- Use Exercise (correct spelling) instead of Excercise
- Keep i64 return types instead of i32
- Keep optimized implementations with rayon
- Keep inputs/ subdirectory structure
- Keep reference parameters (&str) for better performance

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

Author: markkovari