The URL in your address bar IS a persistent link to a specific search (not an individual search result). It will take the user to that result list in Summon, and then they can link to full text from there.
There is also a "permanent link" that appears in each result which will take you to that source in Summon. Click on the "link" icon and copy the permanent link that appears.
Screenshot 1: permanent link icon
Screenshot 2: Copy permanent link
Screenshot 3: Summon search URL link