The @Categories agent exports as Categories.html. Code in the template bstMainPage uses export code to export a list of its children and the titles of their blog-ready children.

The export code from bstMainPage:

^if($Name=="BlogCategories")^
<!-- Name==BlogCategories -->
	<h1 class="post-title">Categories</h1>
	<br>
	<div class="main-toc categories-toc ^if($blogBkgOpt.contains("CARD"))^ article-card^endIf^">
	^children(bstCatsAndPosts)^
	</div>
^endIf^