- Refactored ExecutablePathSearch to remove generic type parameter N and use pre-computed filename candidates instead of single filename.
- Extracted platform-specific candidate_filenames() functions to generate executable filename variants on Windows and Unix-like systems.
- Replaced manual PATH string splitting with std::env::split_paths() for cross-platform path parsing.
- Simplified find_in_path() method to delegate to pathsearch::search_for_executable() instead of custom path searching logic.
- Implemented executable_extensions() function with lazy initialization to parse PATHEXT environment variable on Windows.
- Enhanced executable() method to validate file extensions against known executable extensions instead of returning hardcoded true.