refactor setup script to improve argument handling for continuation flag

setup.sh

@@ -454,10 +454,17 @@ main() {
         log_info "Cloning dotfiles repo..."
         git clone "$GIT_REPO" "$DOTFILES_DIR" || die "Failed to clone dotfiles repository"
     fi
-
-    CONTINUE=$1
-    if [ "$CONTINUE" = "--continue" ]; then
-        log_info "Continuing setup..."
+    
+    if [ -n "${1:-}" ]; then
+        CONTINUE=$1
+        if [ "$CONTINUE" = "--continue" ]; then
+            log_info "Continuing setup..."
+        else
+            warning_prompt
+            prepare_hostname
+            check_selinux
+            install_nix
+        fi
     else
         warning_prompt
         prepare_hostname
@@ -465,6 +472,7 @@ main() {
         install_nix
     fi
 
+
     install_home_manager
     setup_symlinks