Use consistent bash5 style for conditionals and quoting

install/helpers/presentation.sh

@@ -4,10 +4,10 @@ if ! command -v gum &>/dev/null; then
 fi
 
 # Get terminal size from /dev/tty (works in all scenarios: direct, sourced, or piped)
-if [ -e /dev/tty ]; then
+if [[ -e /dev/tty ]]; then
   TERM_SIZE=$(stty size 2>/dev/null </dev/tty)
 
-  if [ -n "$TERM_SIZE" ]; then
+  if [[ -n $TERM_SIZE ]]; then
     export TERM_HEIGHT=$(echo "$TERM_SIZE" | cut -d' ' -f1)
     export TERM_WIDTH=$(echo "$TERM_SIZE" | cut -d' ' -f2)
   else
@@ -25,7 +25,7 @@ export LOGO_PATH="$OMARCHY_PATH/logo.txt"
 export LOGO_WIDTH=$(awk '{ if (length > max) max = length } END { print max+0 }' "$LOGO_PATH" 2>/dev/null || echo 0)
 export LOGO_HEIGHT=$(wc -l <"$LOGO_PATH" 2>/dev/null || echo 0)
 
-export PADDING_LEFT=$((($TERM_WIDTH - $LOGO_WIDTH) / 2))
+export PADDING_LEFT=$(((TERM_WIDTH - LOGO_WIDTH) / 2))
 export PADDING_LEFT_SPACES=$(printf "%*s" $PADDING_LEFT "")
 
 # Tokyo Night theme for gum confirm