Use consistent bash5 style for conditionals and quoting

bin/omarchy-update-branch

@@ -10,7 +10,7 @@ fi
 branch="$1"
 
 # Snapshot before switching branch
-omarchy-snapshot create || [ $? -eq 127 ]
+omarchy-snapshot create || (( $? == 127 ))
 
 if ! git -C "$OMARCHY_PATH" diff --quiet || ! git -C "$OMARCHY_PATH" diff --cached --quiet; then
   stashed=true
@@ -23,7 +23,7 @@ fi
 git -C "$OMARCHY_PATH" switch "$branch"
 
 # Reapply stash if we made one
-if [[ $stashed == true ]]; then
+if [[ $stashed == "true" ]]; then
   if ! git -C "$OMARCHY_PATH" stash pop; then
     echo "⚠️ Conflicts when applying stash — stash kept"
   fi