fix(app): study options saved as they came stay the defaults

A review found three edges of the study options:

- Saving a studyset's study options without changing anything wrote
  the defaults as its own, so it stopped following the person's new
  cards a day and was written in the newer schema older apps skip. It
  now keeps no options of its own.
- The library's badges read the person's new cards a day only when
  something else changed; a change to the setting now refreshes them.
- A person's random order shuffled the whole round, undoing the
  studyset's Reviews first or New first. The reviews and the new cards
  are now each shuffled, the order between them kept.

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

halkyon_learn_flutter/lib/src/feature/study/bloc/study_session_bloc.dart

@@ -122,7 +122,7 @@ class StudySessionBloc(
       for (final group in groups) [for (final card in group) card.id],
     ];
     final queue = _queue(schedules, now);
-    _round = _ordered(queue).take(_options.cardsPerRound).toList();
+    _round = queue.take(_options.cardsPerRound).toList();
     if (_round.isEmpty) {
       final upcoming = [
         for (final schedule in schedules.values) ?schedule.due,
@@ -140,6 +140,9 @@ class StudySessionBloc(
         groups: _groupIds,
         options: _groupOptions,
         order: _order,
+        // Shuffled within reviews and new cards, so that the studyset's
+        // order between them holds.
+        shuffle: _options.effectiveOrder == StudyOrder.random ? _random : null,
         schedules: schedules,
         now: now,
         startOfToday: startOfLocalDay(now),

halkyon_learn_flutter/lib/src/feature/study/model/study_queue.dart

@@ -16,8 +16,10 @@ import 'package:halkyon_learn_flutter/src/feature/study/model/studyset_study_opt
 /// most each studyset's new cards a day. A day is the local one that began at
 /// [startOfToday], and what was reviewed or started in it counts. [order]
 /// (the studied studyset's) says whether the due cards or the new ones come
-/// first, or the new ones spread among the due. When nothing else is due, a
-/// learning card due within [learnAhead] comes early.
+/// first, or the new ones spread among the due; with [shuffle], the due
+/// cards and the new ones are each shuffled first, keeping that order between
+/// them. When nothing else is due, a learning card due within [learnAhead]
+/// comes early.
 List<String> studyQueue({
   required List<List<String>> groups,
   required Map<String, CardSchedule> schedules,
@@ -26,6 +28,7 @@ List<String> studyQueue({
   List<StudysetStudyOptions> options = const [],
   int newPerDay = 20,
   NewCardOrder order = NewCardOrder.reviewsFirst,
+  math.Random? shuffle,
   Duration learnAhead = const Duration(minutes: 20),
 }) {
   DateTime? dueOf(String id) => schedules[id]?.due;
@@ -68,6 +71,10 @@ List<String> studyQueue({
     );
   }
   due.sort(byDue);
+  if (shuffle != null) {
+    due.shuffle(shuffle);
+    fresh.shuffle(shuffle);
+  }
   final queue = switch (order) {
     NewCardOrder.reviewsFirst => [...due, ...fresh],
     NewCardOrder.newFirst => [...fresh, ...due],

halkyon_learn_flutter/lib/src/feature/study/widget/studyset_study_options_sheet.dart

@@ -64,7 +64,13 @@ class _StudyOptionsSheetState() extends State<_StudyOptionsSheet> {
             ),
           const Spacer(),
           FilledButton(
-            onPressed: () => Navigator.of(context).pop((options: _options)),
+            // Saved as they came, the defaults stay the defaults: the
+            // studyset keeps following the person's study settings.
+            onPressed: () => Navigator.of(context).pop((
+              options: widget.current == null && _options == widget.defaults
+                  ? null
+                  : _options,
+            )),
             child: Text(l10n.commonSave),
           ),
         ],

halkyon_learn_flutter/lib/src/feature/studyset/bloc/studyset_list_bloc.dart

@@ -277,6 +277,13 @@ class StudysetListBloc(
       _paths.changes,
       onData: (_) => add(const StudysetListEventProgressRefreshRequested()),
     ),
+    // So do the person's new cards a day, which studysets without study
+    // options of their own follow.
+    emit.onEach(
+      _settings.watch(),
+      onData: (_) => add(const StudysetListEventProgressRefreshRequested()),
+      onError: (_, _) {},
+    ),
     emit.onEach(
       _deletions.watchPending(),
       onData: (pending) {

halkyon_learn_flutter/test/feature/study/model/study_queue_test.dart

@@ -1,3 +1,5 @@
+import 'dart:math' as math;
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:halkyon_learn_flutter/src/feature/study/model/card_schedule.dart';
 import 'package:halkyon_learn_flutter/src/feature/study/model/study_queue.dart';
@@ -196,6 +198,24 @@ void main() {
       expect(queue, ['n1', 'n2', 'due']);
     });
 
+    test('shuffled, the reviews still come before the new cards', () {
+      final queue = studyQueue(
+        groups: [
+          ['d1', 'd2', 'd3', 'n1', 'n2', 'n3'],
+        ],
+        shuffle: math.Random(7),
+        schedules: {
+          for (final (i, id) in ['d1', 'd2', 'd3'].indexed)
+            id: review(overdue.add(Duration(minutes: i))),
+        },
+        now: now,
+        startOfToday: startOfToday,
+      );
+
+      expect(queue.take(3).toSet(), {'d1', 'd2', 'd3'});
+      expect(queue.skip(3).toSet(), {'n1', 'n2', 'n3'});
+    });
+
     test('mixed spreads the new cards evenly among the due ones', () {
       final queue = studyQueue(
         groups: [

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

@@ -425,6 +425,19 @@ void main() {
       );
     });
 
+    testWidgets('saved as they came, the defaults stay the defaults', (
+      tester,
+    ) async {
+      stored('japanese', 'Japanese');
+      await showLibrary(tester);
+
+      await choose(tester, 'Japanese', 'Study options');
+      await tester.tap(find.text('Save'));
+      await tester.pumpAndSettle();
+
+      expect(gateway.writes, isEmpty);
+    });
+
     testWidgets('go back to the defaults with Reset', (tester) async {
       gateway.receiveRemoteChange(
         'japanese',