fix: Restore keyboard focus for key triggers (#2634) (#2639)

- Closes #2634

src/utils/focus.ts

@@ -0,0 +1,14 @@
+/**
+ * Determine whether focus currently rests on an element, or on any of its
+ * descendants (including those inside nested shadow roots).
+ */
+export const isFocusWithin = (element: Element): boolean => {
+  const root = element.getRootNode();
+
+  // Focus is reported per tree, with a shadow host standing in for whatever is
+  // focused inside it, so the element's own tree is the one that will name it.
+  const active =
+    root instanceof Document || root instanceof ShadowRoot ? root.activeElement : null;
+
+  return !!active && element.contains(active);
+};