The chooser's marks are × at the left, tappable once marked

From the development repository at 5252a58.

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

client/kokkoja.css

@@ -439,8 +439,8 @@ h2 {
 
 .chooser_notebooks button.notebook_pick { flex: 1; min-width: 0; text-align: left; }
 
-/* Rows and cards carry a mark at their left, a dot, for deletion (a ×
-   at the right would read as "delete" itself, Andy); marked, they dim. */
+/* Rows and cards carry a mark at their left, ×, for deletion (at the
+   right it would read as "delete" itself, Andy); marked, they dim. */
 .notebook_row { display: flex; gap: 0.3rem; align-items: stretch; }
 .notebook_row.marked button.notebook_pick, .page_slot.marked .page_card { opacity: 0.45; }
 .page_slot { position: relative; display: flex; }
@@ -458,6 +458,10 @@ button.mark {
   left: 0.3rem;
   height: 1.6rem;
   background: white;
+  /* Above the card even when the card's opacity makes it a stacking
+     context painted later: without this, the second tap, to unmark,
+     landed on the dimmed card and loaded the page. */
+  z-index: 1;
 }
 button.mark[aria-pressed="true"] { color: #b42318; }
 button.mark.unavailable { opacity: 0.4; }