Fix bracket highlighting: both ( and ) share open step index

When a tag's open step is evaluated, both its opening and closing
brackets go big+bold together. Previously close ) had the close
step index so it stayed faint until much later.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sx/sx/home-stepper.sx

@@ -90,7 +90,7 @@
                          (do (append! tokens {"text" " " "cls" "" "step" -1})
                              (build-code-tokens a tokens step-ref indent))))))
                    (rest expr))
-                 (append! tokens {"text" ")" "cls" "text-stone-400" "step" (if is-tag (get step-ref "v") open-step)})
+                 (append! tokens {"text" ")" "cls" "text-stone-400" "step" open-step})
                  (when is-tag
                    (dict-set! step-ref "v" (+ (get step-ref "v") 1)))))
            :else nil)))