v3.3.0 - Artifact viewer

Artifact viewer on the status page

Every step row and artifact chip on the live status page is now a link to the
Markdown file it produced. Click one and the right pane switches to a
preformatted viewer — styled <pre>, no Markdown engine — showing the text
with file size, freshness and the owning step's status. Still zero-dependency:
no server, no ports, nothing to refresh.

Full changelog: v3.2.0...v3.3.0