feat(app): the week's rest day sits in its header, beside the day shown

Asked for on 2026-10-07: the rest day moves from below the week into the
week's header, between the day shown and Today and the arrows. From
medium windows on it stays a chip; on a phone, where the date, a chip
and the arrows don't fit in a row, it is a snowflake toggle with "Rest
day" as its tooltip.

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/home/widget/week_overview.dart

@@ -6,10 +6,11 @@ import 'package:intl/intl.dart';
 import 'package:lucide_icons_flutter/lucide_icons.dart';
 import 'package:material_ui/material_ui.dart';
 
-/// The week of [selected] day: the day named on top with going a day back
-/// or on and back to today, Monday to Sunday as boxes with how each stands,
-/// and making the day picked a rest day when it is today or to come and
-/// not studied.
+/// The week of [selected] day: on top the day named, making it a rest day
+/// when it is today or to come and not studied (a chip, on a phone a
+/// snowflake toggle for the room; decided 2026-10-07), and going a day back
+/// or on and back to today; below, Monday to Sunday as boxes with how each
+/// stands.
 class const WeekOverview({
   /// The day picked.
   required final DateTime selected,
@@ -42,6 +43,7 @@ class const WeekOverview({
     final picked = week.where((day) => day.day == selected).firstOrNull;
     final canRest =
         !selected.isBefore(today) && picked?.state != DayState.studied;
+    final resting = restDays.contains(selected);
     return Column(
       crossAxisAlignment: CrossAxisAlignment.stretch,
       children: [
@@ -55,9 +57,34 @@ class const WeekOverview({
                   style: theme.textTheme.titleMedium?.copyWith(
                     fontWeight: FontWeight.w600,
                   ),
+                  maxLines: 1,
+                  overflow: TextOverflow.ellipsis,
                 ),
               ),
             ),
+            if (canRest && beside)
+              Padding(
+                padding: const EdgeInsets.only(left: 8, right: 4),
+                child: FilterChip(
+                  avatar: const Icon(LucideIcons.snowflake, size: 16),
+                  label: Text(l10n.weekRestDay),
+                  selected: resting,
+                  onSelected: (_) => onToggleRestDay(),
+                ),
+              )
+            else if (canRest)
+              IconButton(
+                tooltip: l10n.weekRestDay,
+                isSelected: resting,
+                icon: const Icon(LucideIcons.snowflake),
+                style: resting
+                    ? IconButton.styleFrom(
+                        backgroundColor: theme.colorScheme.secondaryContainer,
+                        foregroundColor: theme.colorScheme.onSecondaryContainer,
+                      )
+                    : null,
+                onPressed: onToggleRestDay,
+              ),
             if (selected != today)
               TextButton(
                 onPressed: () => onSelect(today),
@@ -91,18 +118,6 @@ class const WeekOverview({
               ),
           ],
         ),
-        if (canRest)
-          Padding(
-            padding: const EdgeInsets.only(top: 10),
-            child: Center(
-              child: FilterChip(
-                avatar: const Icon(LucideIcons.snowflake, size: 16),
-                label: Text(l10n.weekRestDay),
-                selected: restDays.contains(selected),
-                onSelected: (_) => onToggleRestDay(),
-              ),
-            ),
-          ),
       ],
     );
   }

halkyon_learn_flutter/test/feature/home/widget/home_screen_test.dart

@@ -25,8 +25,8 @@ void main() {
     settingsGateway = FakeSettingsGateway();
   });
 
-  Future<void> showHome(WidgetTester tester) async {
-    tester.view.physicalSize = const Size(1200, 1600);
+  Future<void> showHome(WidgetTester tester, {double width = 1200}) async {
+    tester.view.physicalSize = Size(width, 1600);
     tester.view.devicePixelRatio = 1;
     addTearDown(tester.view.reset);
     await pumpApp(
@@ -94,6 +94,32 @@ void main() {
     expect(streak(tester), 1);
   });
 
+  testWidgets("the rest day sits in the week's header, beside the day "
+      'shown', (tester) async {
+    await showHome(tester);
+
+    final restDay = tester.getRect(find.text('Rest day'));
+    final previous = tester.getRect(find.byTooltip('Previous day'));
+    expect(restDay.center.dy, closeTo(previous.center.dy, 2));
+    expect(restDay.right, lessThan(previous.left));
+  });
+
+  testWidgets('on a phone, the rest day is a snowflake button in the '
+      "week's header", (tester) async {
+    await showHome(tester, width: 360);
+    expect(find.text('Rest day'), findsNothing);
+
+    final restDay = find.byTooltip('Rest day');
+    expect(
+      tester.getRect(restDay).center.dy,
+      closeTo(tester.getRect(find.byTooltip('Previous day')).center.dy, 2),
+    );
+    await tester.tap(restDay);
+    await tester.pumpAndSettle();
+
+    expect(streak(tester), 1);
+  });
+
   testWidgets('a long press arranges the dashboard: a widget hidden stays '
       'hidden', (tester) async {
     await showHome(tester);