add @testing-library/user-event and create tests for external-knowledge-base/ (#29323)

Co-authored-by: CodingOnStar <hanxujiang@dify.ai>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

web/jest.setup.ts

@@ -1,6 +1,19 @@
 import '@testing-library/jest-dom'
 import { cleanup } from '@testing-library/react'
 
+// Fix for @headlessui/react compatibility with happy-dom
+// headlessui tries to set focus property which is read-only in happy-dom
+if (typeof window !== 'undefined') {
+  // Ensure window.focus is writable for headlessui
+  if (!Object.getOwnPropertyDescriptor(window, 'focus')?.writable) {
+    Object.defineProperty(window, 'focus', {
+      value: jest.fn(),
+      writable: true,
+      configurable: true,
+    })
+  }
+}
+
 afterEach(() => {
   cleanup()
 })