The new 6.10 release features Content Server FTS!
What delighted me more about it is that this feature made it possible to add Calibre FTS to any web browser context menu, for searches on text selections. For example, in classic Mozilla Browsers, this url will work:
http://127.0.0.1:8080/#fts_panel=search&fts_query=%22{searchTerms}%22&ft s_use_stemming=n&isTrusted=true&library_id=Calibre _Library&mode=book_list&panel=fts
Thanks so much Kovid!