feat(library): Import and Refresh behind one menu button

The library's top bar had a button each for Import and Refresh. Pulling
the list down refreshes too, and is the quicker way on a phone, so both
now sit in a menu ("Library options"), leaving the bar to Search.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/test/feature/studyset/widget/library_screen_test.dart

@@ -132,13 +132,15 @@ void main() {
     expect(find.text('Japanese'), findsOneWidget);
   });
 
-  testWidgets('Refresh syncs, from the app bar and by pulling the list '
+  testWidgets('Refresh syncs, from the menu and by pulling the list '
       'down', (tester) async {
     stored('japanese', 'Japanese');
     await showLibrary(tester);
     final before = syncs;
 
-    await tester.tap(find.byTooltip('Refresh'));
+    await tester.tap(find.byTooltip('Library options'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('Refresh'));
     await tester.pumpAndSettle();
     expect(syncs, before + 1);