Enable home-manager on WSL, importing the shared home.nix config.
Remove duplicate packages and env vars from wsl.nix that are now
provided by home-manager (git, ripgrep, fzf, direnv, etc.).
- Remove trailing whitespaces from all .nix files
- Remove trailing whitespaces from shell scripts
- Remove trailing whitespaces from README files
- Improves code consistency and follows best practices
- Add EDITOR and VISUAL environment variables to fish shell init
- Add system-level EDITOR and VISUAL variables for macOS and WSL
- Ensures nvim is used as default editor for git, system tools, and applications
- Maintains existing neovim defaultEditor configuration
