Better yet, just use Node.

src/004-base/domPassage.js

@@ -4,7 +4,7 @@
 App.DomPassage = class extends Passage {
 	/**
 	 * @param {string} title
-	 * @param {function():(DocumentFragment|HTMLElement)} callback
+	 * @param {function():Node} callback
 	 * @param {string[]} tags
 	 */
 	constructor(title, callback, tags = []) {
@@ -18,7 +18,7 @@ App.DomPassage = class extends Passage {
 	}
 
 	/**
-	 * @returns {DocumentFragment|HTMLElement}
+	 * @returns {Node}
 	 */
 	render() {
 		return this.callback();