On the summarisers page it should offer the ability to export the summary. The markup is already pretty minimal and works well with copy-paste. It could be with or without some header than contains the URL of the original doc, timestamp, and/or link to the summariser.
With document discussion, as Kagi doesn't (and shouldn't) save conversations it should instead offer the ability to export and save them yourself. This could be in the form of a markdown document using quote blocks for the AI response. It would also be nice to include the original document URL, timestamp, and/or other relevant information.