Add kitty.conf to dotfiles and set as default terminal

- Add .config/kitty/kitty.conf
- setup.sh now sets kitty as default terminal via update-alternatives
- README updated to include kitty.conf

README.md

@@ -8,6 +8,7 @@ My personal dotfiles for quick setup on new machines. Change once, update everyw
 |------|-------------|
 | `.bashrc` | Bash configuration with custom prompt, aliases, lazy-loaded conda/nvm |
 | `.vimrc` | Vim configuration with clipboard support, syntax highlighting, and sensible defaults |
+| `.config/kitty/kitty.conf` | kitty terminal config with tmux-style splits |
 | `setup.sh` | Bootstrap script for new Debian-like machines |
 
 ## Quick Install on a New Machine