feat(review): request a store review after a 3-star win, once

Adds an in-app review prompt gated by ReviewPromptPolicy: only after a
3-star stage win, once the player has cleared >=5 stages, at most once
ever (persisted reviewRequested flag). ReviewService swallows all
failures and only burns the one-shot when the store actually shows the
sheet, so an unavailable store retries on a later win. StoreReviewer
wraps in_app_review behind a Reviewer seam so unit tests skip platform
channels. 13 new tests; full suite 194 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/services/review_prompt_policy_test.dart

@@ -0,0 +1,66 @@
+import 'package:block_seasons/services/review_prompt_policy.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  const policy = ReviewPromptPolicy(); // minStagesWon: 5, requiredStars: 3
+
+  test('asks for a review on a 3-star win once enough stages are cleared', () {
+    expect(
+      policy.shouldRequest(
+        alreadyRequested: false,
+        won: true,
+        stars: 3,
+        totalStagesWon: 5,
+      ),
+      isTrue,
+    );
+  });
+
+  test('never asks again once a review has been requested', () {
+    expect(
+      policy.shouldRequest(
+        alreadyRequested: true,
+        won: true,
+        stars: 3,
+        totalStagesWon: 20,
+      ),
+      isFalse,
+    );
+  });
+
+  test('does not ask after a loss', () {
+    expect(
+      policy.shouldRequest(
+        alreadyRequested: false,
+        won: false,
+        stars: 0,
+        totalStagesWon: 10,
+      ),
+      isFalse,
+    );
+  });
+
+  test('does not ask before enough stages are cleared', () {
+    expect(
+      policy.shouldRequest(
+        alreadyRequested: false,
+        won: true,
+        stars: 3,
+        totalStagesWon: 4, // one short of the 5-stage gate
+      ),
+      isFalse,
+    );
+  });
+
+  test('does not ask on a win below the star bar (2 stars)', () {
+    expect(
+      policy.shouldRequest(
+        alreadyRequested: false,
+        won: true,
+        stars: 2,
+        totalStagesWon: 10,
+      ),
+      isFalse,
+    );
+  });
+}

test/services/review_service_test.dart

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+import 'package:block_seasons/data/save_repository.dart';
+import 'package:block_seasons/services/review_service.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class _FakeReviewer implements Reviewer {
+  _FakeReviewer({this.available = true, this.throwOnRequest = false});
+
+  bool available;
+  bool throwOnRequest;
+  int requestCalls = 0;
+
+  @override
+  Future<bool> isAvailable() async => available;
+
+  @override
+  Future<void> requestReview() async {
+    requestCalls++;
+    if (throwOnRequest) throw Exception('store unavailable');
+  }
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  Future<SaveRepository> repoWithStagesCleared(int n) async {
+    SharedPreferences.setMockInitialValues({});
+    final repo = SaveRepository(await SharedPreferences.getInstance());
+    for (var i = 0; i < n; i++) {
+      await repo.recordResult(
+          seasonId: 'season_001', stageId: 's$i', stars: 3, score: 100);
+    }
+    return repo;
+  }
+
+  test('requests a review and marks the flag on a qualifying win', () async {
+    final repo = await repoWithStagesCleared(5);
+    final reviewer = _FakeReviewer();
+    final service = ReviewService(save: repo, reviewer: reviewer);
+
+    await service.maybeRequestAfterWin(stars: 3);
+
+    expect(reviewer.requestCalls, 1);
+    expect(repo.reviewRequested, isTrue);
+  });
+
+  test('never requests twice', () async {
+    final repo = await repoWithStagesCleared(5);
+    await repo.markReviewRequested();
+    final reviewer = _FakeReviewer();
+    final service = ReviewService(save: repo, reviewer: reviewer);
+
+    await service.maybeRequestAfterWin(stars: 3);
+
+    expect(reviewer.requestCalls, 0);
+  });
+
+  test('does not request when the policy is not satisfied', () async {
+    final repo = await repoWithStagesCleared(2); // below the 5-stage gate
+    final reviewer = _FakeReviewer();
+    final service = ReviewService(save: repo, reviewer: reviewer);
+
+    await service.maybeRequestAfterWin(stars: 3);
+
+    expect(reviewer.requestCalls, 0);
+    expect(repo.reviewRequested, isFalse);
+  });
+
+  test('does not burn the one-shot when the store is unavailable', () async {
+    final repo = await repoWithStagesCleared(5);
+    final reviewer = _FakeReviewer(available: false);
+    final service = ReviewService(save: repo, reviewer: reviewer);
+
+    await service.maybeRequestAfterWin(stars: 3);
+
+    expect(reviewer.requestCalls, 0);
+    expect(repo.reviewRequested, isFalse, reason: 'retry on a later win');
+  });
+
+  test('swallows reviewer errors without throwing', () async {
+    final repo = await repoWithStagesCleared(5);
+    final reviewer = _FakeReviewer(throwOnRequest: true);
+    final service = ReviewService(save: repo, reviewer: reviewer);
+
+    // Must complete normally despite the plugin throwing.
+    await service.maybeRequestAfterWin(stars: 3);
+    expect(reviewer.requestCalls, 1);
+  });
+}