feat: session content sync trigger and newest-season selection

Add seasonRefreshProvider (once-per-session FutureProvider) and activeSeason()
helper; HomeScreen listens and invalidates seasonsProvider when new packs arrive;
season_map_screen and season_title_screen switch from list.first to activeSeason.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/state/providers.dart

@@ -44,6 +44,16 @@ final seasonsProvider = FutureProvider<List<SeasonPack>>(
   (ref) => ref.read(contentRepositoryProvider).availableSeasons(),
 );
 
+/// One background content sync per app session. Home listens and refreshes
+/// the season list when new packs arrived.
+final seasonRefreshProvider = FutureProvider<bool>(
+  (ref) => ref.read(contentRepositoryProvider).refresh(),
+);
+
+/// The season players land in by default: the newest available.
+/// (availableSeasons is sorted by seasonId ascending.)
+SeasonPack activeSeason(List<SeasonPack> seasons) => seasons.last;
+
 final streakProvider = NotifierProvider<StreakNotifier, StreakState>(
   StreakNotifier.new,
 );

lib/ui/screens/home_screen.dart

@@ -21,6 +21,11 @@ class HomeScreen extends ConsumerWidget {
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
+    ref.listen(seasonRefreshProvider, (_, next) {
+      if (next is AsyncData<bool> && next.value == true) {
+        ref.invalidate(seasonsProvider);
+      }
+    });
     final l10n = AppLocalizations.of(context)!;
     final streak = ref.watch(streakProvider);
     final best = ref.watch(endlessBestProvider);

lib/ui/screens/season_map_screen.dart

@@ -21,7 +21,7 @@ class SeasonMapScreen extends ConsumerWidget {
       loading: () =>
           const Scaffold(body: Center(child: CircularProgressIndicator())),
       error: (e, _) => Scaffold(body: Center(child: Text('$e'))),
-      data: (list) => _JourneyMap(pack: list.first),
+      data: (list) => _JourneyMap(pack: activeSeason(list)),
     );
   }
 }

lib/ui/screens/season_title_screen.dart

@@ -63,7 +63,7 @@ class _SeasonTitleScreenState extends ConsumerState<SeasonTitleScreen> {
           _auto?.cancel();
           _auto = Timer(const Duration(milliseconds: 1600), _go);
         }
-        final pack = list.first;
+        final pack = activeSeason(list);
         final locale = Localizations.localeOf(context).languageCode;
         final number = int.tryParse(pack.seasonId.split('_').last) ?? 1;
         return GestureDetector(

test/state/season_refresh_test.dart

@@ -0,0 +1,59 @@
+import 'package:block_seasons/data/content_repository.dart';
+import 'package:block_seasons/game/models/season.dart';
+import 'package:block_seasons/game/models/stage.dart';
+import 'package:block_seasons/state/providers.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+class _FakeRepo extends ContentRepository {
+  _FakeRepo(this.result);
+  final bool result;
+  int calls = 0;
+
+  @override
+  Future<bool> refresh() async {
+    calls++;
+    return result;
+  }
+}
+
+SeasonPack _pack(String id) => SeasonPack(
+      schemaVersion: 1,
+      seasonId: id,
+      version: 1,
+      title: const {'en': 'Test Season', 'ko': '테스트 시즌'},
+      theme: SeasonTheme.fallback,
+      stages: [
+        StageConfig(
+          id: 's1',
+          seed: 1,
+          moveLimit: 10,
+          preset: const [],
+          objectives: const [],
+          stars: const StarThresholds(twoMovesLeft: 2, threeMovesLeft: 4),
+          generatorProfile: 'mid',
+        ),
+      ],
+    );
+
+void main() {
+  test('seasonRefreshProvider runs refresh once and exposes the result',
+      () async {
+    final repo = _FakeRepo(true);
+    final container = ProviderContainer(
+      overrides: [contentRepositoryProvider.overrideWithValue(repo)],
+    );
+    addTearDown(container.dispose);
+
+    expect(await container.read(seasonRefreshProvider.future), isTrue);
+    // Re-reading does not re-run (FutureProvider caches).
+    expect(await container.read(seasonRefreshProvider.future), isTrue);
+    expect(repo.calls, 1);
+  });
+
+  test('activeSeason picks the newest by id', () {
+    final p1 = _pack('season_001');
+    final p2 = _pack('season_002');
+    expect(activeSeason([p1, p2]).seasonId, 'season_002');
+  });
+}