(defcomp
  ()
  (~docs/page
    :title "Effect + Cleanup: Stopwatch"
    (p
      "Effects can return cleanup functions. This stopwatch starts a "
      (code "set-interval")
      " — the cleanup clears it when the running signal toggles off.")
    (~reactive-islands/index/demo-stopwatch)
    (~docs/code
      :src (highlight
        (component-source "~reactive-islands/index/demo-stopwatch")
        "lisp"))
    (p
      "Three effects, each tracking different signals. The timer effect's cleanup fires before each re-run — toggling "
      (code "running")
      " off clears the interval. No hook rules: effects can appear anywhere, in any order.")))
