facet-html drops valid HTML5 custom elements during an HTML parse/serialize roundtrip. When parsing markup…

facet-html drops valid HTML5 custom elements during an HTML parse/serialize roundtrip. When parsing markup…: a task in LegoFlow-SWE (Harbor dataset). Repro: Input: html <pre <code class="language-rust" <a-k fn</a-k <a-f main</a-f () { <a-fm println!</a-fm (<a-s "Hello, world!"</a-s ); }</code </pre