feat: give assistants each page as markdown

The build writes <page>/index.md beside each page, named in its head,
and llms-full.txt. llms.txt and the setup skill say how to answer from
the site, not from memory, and the setup_bios_files WebMCP tool gives a
setup's folder and exact file names from the picker data.

.github/workflows/deploy-site.yml

@@ -47,6 +47,7 @@ on:
       - "scripts/safeparse.py"
       - "scripts/sect233r1.py"
       - "scripts/siteagents.py"
+      - "scripts/site_markdown.py"
       - "scripts/sitebootstrap.py"
       - "scripts/sitecollection.py"
       - "scripts/sitediagrams.py"