Show dialogue choices in a box above the text box (#67)

YES/NO, menus and amount boxes float above the text box on the right, as in
the original. The cursor marker reserves its width so the box keeps its size
as the cursor moves, and the app-made CANCEL button under menus is removed
because B leaves the menu.

Closes #67 [no-card]

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

src/main.ts

@@ -291,10 +291,8 @@ function showChoice(choice: Choice | undefined) {
         return option;
       }),
     );
-    container.replaceChildren(
-      list,
-      button("CANCEL", undefined, () => runtime.choose(-1)),
-    );
+    // As in the original there is no CANCEL entry: B leaves the menu.
+    container.replaceChildren(list);
     // On a small screen the box scrolls; keep the highlighted entry in view.
     list
       .querySelector('[aria-selected="true"]')