feat: add Nerd Font installation, Yazi file manager, and themed Yazi config

- Install JetBrainsMono Nerd Font for icons across all TUI tools
- Add Yazi as terminal file manager with themed config per colorscheme
- Add write_yazi_config() to all 5 theme files
- Theme switcher (archduino-theme) now also updates Yazi
- Add 'y' alias for yazi in shell config
- Update step numbering (9 -> 11 steps) and README

install.sh

@@ -75,10 +75,12 @@ fi
 
 # ── Run install steps ───────────────────────────────────────────
 source "$SCRIPT_DIR/lib/packages.sh"
+source "$SCRIPT_DIR/lib/fonts.sh"
 source "$SCRIPT_DIR/lib/zsh.sh"
 source "$SCRIPT_DIR/lib/starship.sh"
 source "$SCRIPT_DIR/lib/zellij.sh"
 source "$SCRIPT_DIR/lib/neovim.sh"
+source "$SCRIPT_DIR/lib/yazi.sh"
 source "$SCRIPT_DIR/lib/arduino.sh"
 source "$SCRIPT_DIR/lib/git.sh"
 source "$SCRIPT_DIR/lib/scaffold.sh"