The chooser's marks are dots at the left

From the development repository at 06a7ffb.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/host.md

@@ -248,7 +248,7 @@ A lesson might go: **New**, **Image** for the exercise, work, **New**
 for a point of grammar, work, **Notebooks** to return to the exercise.
 
 The same chooser deletes.  Every page card and every notebook in the
-list carries a small × mark; a tap marks it, a second tap unmarks it,
+list carries a small dot at its left; a tap marks it with a tick, a second tap unmarks it,
 and a marked notebook goes with every page in it.  As soon as something
 is marked, a **Delete** button in the chooser's header says how much:
 "Delete 3 pages?", "Delete 1 notebook and 3 pages?".  The first press