All of the mid-session and step-up auth work

clients/web/src/utils/browserTabVisibility.ts

@@ -0,0 +1,20 @@
+/** True when this browser tab is the foreground tab (Page Visibility API). */
+export function isBrowserTabVisible(): boolean {
+  return (
+    typeof document !== "undefined" && document.visibilityState === "visible"
+  );
+}
+
+/** Subscribe to this browser tab becoming visible. Returns an unsubscribe function. */
+export function onBrowserTabVisible(callback: () => void): () => void {
+  if (typeof document === "undefined") {
+    return () => {};
+  }
+  const handler = (): void => {
+    if (document.visibilityState === "visible") {
+      callback();
+    }
+  };
+  document.addEventListener("visibilitychange", handler);
+  return () => document.removeEventListener("visibilitychange", handler);
+}