style: normalize whitespace and line endings in shell scripts

- Standardize indentation and spacing across install.sh and lib files
- Fix line ending inconsistencies for better cross-platform compatibility
- Improve curl flag usage in neovim.sh (-kLo with explicit temp path)
- Add theme persistence functionality to remember user's colorscheme choice

These changes improve code consistency and add the ability to save/restore
the selected theme across sessions.

lib/themes.sh

@@ -2,29 +2,53 @@
 # Theme selection — sources the chosen theme file
 
 THEMES_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/themes"
+THEME_SAVE_FILE="$HOME/.config/archduino/theme"
 
 THEME_FILES=(gruvbox catppuccin tokyonight nord dracula)
 
 select_theme() {
+  # Load previously saved theme as default
+  local saved_theme="" default_idx=1
+  if [[ -f "$THEME_SAVE_FILE" ]]; then
+    saved_theme=$(cat "$THEME_SAVE_FILE")
+    for idx in "${!THEME_FILES[@]}"; do
+      if [[ "${THEME_FILES[$idx]}" == "$saved_theme" ]]; then
+        default_idx=$((idx + 1))
+        break
+      fi
+    done
+  fi
+
   echo "  Select colorscheme:"
   echo ""
 
   local i=1
   for t in "${THEME_FILES[@]}"; do
     source "$THEMES_DIR/$t.sh"
-    printf "    %d) %s\n" "$i" "$THEME_DISPLAY_NAME"
+    if [[ $i -eq $default_idx && -n "$saved_theme" ]]; then
+      printf "    %d) %s (current)\n" "$i" "$THEME_DISPLAY_NAME"
+    else
+      printf "    %d) %s\n" "$i" "$THEME_DISPLAY_NAME"
+    fi
     i=$((i + 1))
   done
 
   echo ""
-  read -rp "  Choice [1-${#THEME_FILES[@]}]: " theme_choice
+  read -rp "  Choice [1-${#THEME_FILES[@]}] (default: $default_idx): " theme_choice
 
-  # Default to 1 (Gruvbox) for invalid input
-  if [[ ! "$theme_choice" =~ ^[0-9]+$ ]] || ((theme_choice < 1 || theme_choice > ${#THEME_FILES[@]})); then
-    theme_choice=1
+  # Default to saved theme (or Gruvbox) for empty/invalid input
+  if [[ -z "$theme_choice" ]]; then
+    theme_choice=$default_idx
+  elif [[ ! "$theme_choice" =~ ^[0-9]+$ ]] || ((theme_choice < 1 || theme_choice > ${#THEME_FILES[@]})); then
+    theme_choice=$default_idx
   fi
 
   local selected="${THEME_FILES[$((theme_choice - 1))]}"
   source "$THEMES_DIR/$selected.sh"
+
+  # Persist choice for next run
+  mkdir -p "$(dirname "$THEME_SAVE_FILE")"
+  echo "$selected" > "$THEME_SAVE_FILE"
+
   info "Selected theme: $THEME_DISPLAY_NAME"
 }