refactor(iframe): [PKG-IFRAME-04] preserve types across module consumers

test/types/iframe-commonjs.cts

@@ -0,0 +1,16 @@
+/* eslint-disable ts/no-require-imports -- Verify native TypeScript CommonJS constructor imports. */
+import Iframe = require('artplayer-tool-iframe')
+import Legacy = require('artplayer-tool-iframe/legacy')
+
+declare const frame: HTMLIFrameElement
+const option: Iframe.Option = { iframe: frame, url: '/frame' }
+const tool: Iframe = new Iframe(option)
+const old: Legacy = new Legacy(option)
+const message: Iframe.Message<number> = { type: 'custom', data: 2 }
+tool.postMessage(message)
+old.commit(() => {
+  return 2
+})
+// @ts-expect-error Direct CommonJS constructor has no default namespace.
+const wrong = Iframe.default
+void wrong