Update deploy-site.sh to use oxcaml switch and install all packages
Switch from default to 5.2.0+ox opam switch. Use `dune install` to
install all workspace packages (not just plugins) so that jtw opam
can find transitive dependencies like js_top_worker-widget and odoc.model.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>