Use Omarchy command helpers consistently

bin/omarchy-snapshot

@@ -13,7 +13,7 @@ if [[ -z $COMMAND ]]; then
   exit 1
 fi
 
-if ! command -v snapper &>/dev/null; then
+if omarchy-cmd-missing snapper; then
   exit 127 # omarchy-update can use this to just ignore if snapper is not available
 fi