MDWiki might meet your needs.
MDwiki is a CMS/Wiki completely built in HTML5/Javascript and runs 100% on the client. No special software installation or server side processing is required. Just upload the mdwiki.html shipped with MDwiki into the same directory as your markdown files and you are good to go!
It's under active development and seems worth a look. It doesn't (appear to) have any automatic indexing but other that it's meeting my needs.