Use consistent bash5 style for conditionals and quoting

bin/omarchy-theme-set-obsidian

@@ -4,15 +4,15 @@
 
 CURRENT_THEME_DIR="$HOME/.config/omarchy/current/theme"
 
-[ -f "$CURRENT_THEME_DIR/obsidian.css" ] || exit 0
+[[ -f $CURRENT_THEME_DIR/obsidian.css ]] || exit 0
 
 jq -r '.vaults | values[].path' ~/.config/obsidian/obsidian.json 2>/dev/null | while read -r vault_path; do
-  [ -d "$vault_path/.obsidian" ] || continue
+  [[ -d $vault_path/.obsidian ]] || continue
 
   theme_dir="$vault_path/.obsidian/themes/Omarchy"
   mkdir -p "$theme_dir"
 
-  [ -f "$theme_dir/manifest.json" ] || cat >"$theme_dir/manifest.json" <<'EOF'
+  [[ -f $theme_dir/manifest.json ]] || cat >"$theme_dir/manifest.json" <<'EOF'
 {
   "name": "Omarchy",
   "version": "1.0.0",