Wiki mermaid: entity-encode angle brackets and serve over HTTP, not file://

Porting standalone mermaid HTML pages into the errata Developer Wiki (docs/reference/, rendered by docs/reference/_wiki-template.html via client-side marked.js + mermaid@11). Two failures when authoring/verifying a native wiki .md page: (1) headless verification over file:// showed "Error loading document" and zero mermaid/tables rendered; (2) a mermaid sequenceDiagram message containing literal <nonce> (as in push provenance-<nonce>) would be silently truncated because the wiki template injects the fenced code as innerHTML. The wiki template does fetch(mdFile).then(...content.innerHTML = marked.parse(md)). (1) Under file:// the fetch is blocked by CORS ("Cross origin requests are only supported for protocol schemes: chrome, http, https..."), so the page never renders — must serve the built site over HTTP (python3 -m http.server) and navigate via http://localhost. (2) The template's custom marked renderer.code returns '<div class="mermaid">' + rawText + '</div>' WITHOUT HTML-escaping for mermaid blocks. So any <...> in the mermaid source is parsed by the browser as an HTML tag before mermaid reads it, dropping the token from textContent. The imago source pages had used HTML entities (<nonce>) precisely because they were raw HTML; the same trick is needed in the markdown fence.