html_export_url_base

Html export should accept an optional urlBase mount prefix ( for example `/spec` or `/reqlan/spec` ).
When set, page and asset hrefs must be root-relative under that prefix so static hosts resolve correctly whether the directory URL includes a trailing slash.
When omitted, exports keep document-relative hrefs suitable for local folder browsing.
Applies across html_export_internal_links and html_export_graph_links; site embed consumption: spec_html_export.
Often paired with html_export_header_link when the export is mounted under a parent static site.

Status: done

Interactive page: html_export_url_base