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

- Closes #2634

tests/utils/focus.test.ts

@@ -0,0 +1,70 @@
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { isFocusWithin } from '../../src/utils/focus';
+
+// @vitest-environment jsdom
+describe('isFocusWithin', () => {
+  const createFocusableElement = (parent: Node): HTMLElement => {
+    const element = document.createElement('div');
+    element.setAttribute('tabindex', '0');
+    parent.appendChild(element);
+    return element;
+  };
+
+  afterEach(() => {
+    document.body.replaceChildren();
+  });
+
+  it('should return false without focus', () => {
+    const element = createFocusableElement(document.body);
+
+    expect(isFocusWithin(element)).toBeFalsy();
+  });
+
+  it('should return false when focus is elsewhere', () => {
+    const element = createFocusableElement(document.body);
+    createFocusableElement(document.body).focus();
+
+    expect(isFocusWithin(element)).toBeFalsy();
+  });
+
+  it('should return true when the element itself has focus', () => {
+    const element = createFocusableElement(document.body);
+    element.focus();
+
+    expect(isFocusWithin(element)).toBeTruthy();
+  });
+
+  it('should return true when a child has focus', () => {
+    const element = createFocusableElement(document.body);
+    createFocusableElement(element).focus();
+
+    expect(isFocusWithin(element)).toBeTruthy();
+  });
+
+  it('should return true when a child within nested shadow roots has focus', () => {
+    const element = createFocusableElement(document.body);
+    const outerShadow = element.attachShadow({ mode: 'open' });
+    const inner = createFocusableElement(outerShadow);
+    const innerShadow = inner.attachShadow({ mode: 'open' });
+
+    createFocusableElement(innerShadow).focus();
+
+    expect(isFocusWithin(element)).toBeTruthy();
+  });
+
+  it('should return true when the element is itself within a shadow root', () => {
+    const host = createFocusableElement(document.body);
+    const element = createFocusableElement(host.attachShadow({ mode: 'open' }));
+
+    createFocusableElement(element.attachShadow({ mode: 'open' })).focus();
+
+    expect(isFocusWithin(element)).toBeTruthy();
+  });
+
+  it('should return false when the element is not attached to a document', () => {
+    const element = document.createElement('div');
+
+    expect(isFocusWithin(element)).toBeFalsy();
+  });
+});