feat: update deploy script and workspace for site content
Switch dune-workspace from --shell docsite to --shell jon-shell so the
jon-site package renders with the correct shell layout. Update
deploy-site.sh to document the jon-site integration, add the
odoc-jon-shell prerequisite, and list site content key pages.
The site content (blog, notebooks, reference) is picked up
automatically by `dune build @doc` via the jon-site documentation
stanza. No interactive cells exist in site content yet, so the
universe deployment path remains unchanged.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>