Keep is a button on the show's page, a plus, not a switch in its settings (#280)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/configuration.md

@@ -166,7 +166,7 @@ new in a year), with nobody subscribed and no file on disk, is removed from the
 
 Feeds derived from a subscribed OPML are **not** in the catalogue: the OPML is the source of truth
 and they are re-derived on every scan. Editing one in the UI promotes it to a catalogue entry. So
-does Keep, in a show's settings, for whoever turns it on (`kept` on their subscription, #280): when
+does Keep, the plus on a show's page, for whoever turns it on (`kept` on their subscription, #280): when
 the OPML stops listing the show, or nobody subscribes to the OPML any more, it becomes a catalogue
 entry outside the OPML instead of going, and stays on the lists of those who kept it. Anyone who
 had it only through the OPML loses it as before. Leaving the OPML yourself keeps what you kept.