feat(exercice): état d'exécution Chrono suivant prêt (ticket #78)

Ajoute l'état "Chrono suivant prêt" sur workout_execution_screen.dart
pour l'auto-enchaînement des chronos d'étapes. Corrige
_startCurrentStepTimerIfNeeded() qui forçait à tort startTimer() : il
se contente maintenant de rafraîchir le ticker d'affichage, laissant
le backend (#76) seul décisionnaire du démarrage automatique ou de
l'attente du chrono suivant. flutter pub get OK, dart format appliqué
(aucun changement), analyze propre (mêmes infos préexistantes),
153/153 tests verts (dont le test de non-régression pour
l'enchaînement automatique activé par défaut), build APK debug
validé. Dernier ticket de développement du chantier
"auto-enchaînement des chronos d'étapes" (#73) — il ne reste que la
QA finale (#79).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/presentation/workout_execution_screen.dart

@@ -740,16 +740,9 @@ final class _WorkoutExecutionScreenState extends State<WorkoutExecutionScreen> {
     }
   }
 
-  Future<void> _startCurrentStepTimerIfNeeded() async {
+  Future<void> _startCurrentStepTimerIfNeeded() {
-    final view = _stepProgress;
+    _refreshStepTicker();
-    final step = view?.currentStep;
+    return Future<void>.value();
-    if (view == null ||
-        step == null ||
-        step.type != ExerciseStepType.time ||
-        view.state.status == ActiveExerciseStepProgressStatus.runningTimer) {
-      return;
-    }
-    await _startCurrentStepTimer();
   }
 
   Future<void> _completeCurrentStep() async {
@@ -1537,6 +1530,7 @@ final class _StepSequencePanel extends StatelessWidget {
                 running:
                     view.state.status ==
                     ActiveExerciseStepProgressStatus.runningTimer,
+                readyToStart: _isNextTimedStepReady(view),
                 onStartTimer: onStartTimer,
               )
             else
@@ -1590,12 +1584,14 @@ final class _TimedStepBody extends StatelessWidget {
     required this.step,
     required this.remainingLabel,
     required this.running,
+    required this.readyToStart,
     required this.onStartTimer,
   });
 
   final ExerciseStep step;
   final String remainingLabel;
   final bool running;
+  final bool readyToStart;
   final VoidCallback onStartTimer;
 
   @override
@@ -1615,10 +1611,22 @@ final class _TimedStepBody extends StatelessWidget {
         ),
         if (!running) ...[
           const SizedBox(height: 12),
+          if (readyToStart) ...[
+            Text(
+              'Chrono suivant prêt',
+              textAlign: TextAlign.center,
+              style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                color: Theme.of(context).colorScheme.primary,
+              ),
+            ),
+            const SizedBox(height: 8),
+          ],
           FilledButton.icon(
             onPressed: onStartTimer,
             icon: const Icon(Icons.play_arrow),
-            label: const Text('Démarrer la séquence'),
+            label: Text(
+              readyToStart ? 'Démarrer le chrono' : 'Démarrer la séquence',
+            ),
           ),
         ],
       ],
@@ -1626,6 +1634,22 @@ final class _TimedStepBody extends StatelessWidget {
   }
 }
 
+bool _isNextTimedStepReady(ActiveExerciseStepProgressView view) {
+  final step = view.currentStep;
+  if (step == null ||
+      step.type != ExerciseStepType.time ||
+      view.state.status != ActiveExerciseStepProgressStatus.stoppedTimer) {
+    return false;
+  }
+  return view.results.any((result) {
+    if (result.passageIndex < view.state.currentPassageIndex) {
+      return true;
+    }
+    return result.passageIndex == view.state.currentPassageIndex &&
+        result.stepIndex < view.state.currentStepIndex;
+  });
+}
+
 final class _RepsStepBody extends StatelessWidget {
   const _RepsStepBody({required this.step, required this.onCompleteStep});
 

test/presentation/workout_execution_screen_test.dart

@@ -1202,7 +1202,7 @@ void main() {
 
     await tester.tap(find.text('Démarrer la séquence'));
     await tester.pump();
-    clock.value = DateTime.utc(2026, 7, 17, 12, 0, 1);
+    clock.value = DateTime.utc(2026, 7, 17, 12, 0, 1, 200);
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump();
 
@@ -1211,9 +1211,86 @@ void main() {
     expect(find.text('ÉTAPE 2 / 2'), findsOneWidget);
     expect(find.text('Droite'), findsOneWidget);
     expect(find.text('00:02'), findsOneWidget);
+    expect(
+      repository.stepProgressStates.single.status,
+      ActiveExerciseStepProgressStatus.runningTimer,
+    );
     expect(audio.longBeeps, 1);
   });
 
+  testWidgets(
+    'chrono suivant prêt attend un démarrage manuel quand l’enchaînement est désactivé',
+    (tester) async {
+      await tester.binding.setSurfaceSize(const Size(400, 1600));
+      addTearDown(() => tester.binding.setSurfaceSize(null));
+
+      final clock = _FakeClock(DateTime.utc(2026, 7, 17, 12));
+      final repository = _FakeActiveSessionRepository();
+      final session = ActiveWorkoutSession(
+        metadata: _metadata('session-1'),
+        sourceWorkoutTemplateId: 'template-1',
+        status: ActiveWorkoutStatus.running,
+        startedAt: DateTime.utc(2026, 7, 17, 12),
+        lastPersistedAt: DateTime.utc(2026, 7, 17, 12),
+        elapsedActiveMs: 0,
+        currentProgramIndex: 0,
+        currentExerciseIndex: 0,
+        currentSetIndex: 0,
+        resolvedTemplateSnapshotJson: _sessionSnapshot(
+          targetReps: 1,
+          autoStartNextTimedStep: false,
+          exerciseSteps: [
+            _step('step-1', 0, 'Gauche', ExerciseStepType.time, 1),
+            _step('step-2', 1, 'Droite', ExerciseStepType.time, 2),
+          ],
+        ),
+      );
+      repository.session = session;
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: WorkoutExecutionScreen(
+            initialSession: session,
+            activeUseCases: _activeUseCases(repository, clock),
+            stepUseCases: _stepUseCases(repository, clock),
+            stepAudioCuePlayer: _FakeStepAudioCuePlayer(),
+            closeUseCase: _closeUseCase(repository, clock),
+            historyUseCases: _historyUseCases(clock),
+            workoutTemplateUseCases: _workoutTemplateUseCases(),
+          ),
+        ),
+      );
+      await tester.pump();
+
+      await tester.tap(find.text('Démarrer la séquence'));
+      await tester.pump();
+      clock.value = DateTime.utc(2026, 7, 17, 12, 0, 1, 200);
+      await tester.pump(const Duration(milliseconds: 200));
+      await tester.pump();
+
+      expect(repository.stepResults.single.stepIndex, 0);
+      expect(find.text('ÉTAPE 2 / 2'), findsOneWidget);
+      expect(find.text('Droite'), findsOneWidget);
+      expect(find.text('00:02'), findsOneWidget);
+      expect(find.text('Chrono suivant prêt'), findsOneWidget);
+      expect(find.text('Démarrer le chrono'), findsOneWidget);
+      expect(
+        repository.stepProgressStates.single.status,
+        ActiveExerciseStepProgressStatus.stoppedTimer,
+      );
+      expect(repository.stepProgressStates.single.startedAt, isNull);
+
+      await tester.tap(find.text('Démarrer le chrono'));
+      await tester.pump();
+
+      expect(
+        repository.stepProgressStates.single.status,
+        ActiveExerciseStepProgressStatus.runningTimer,
+      );
+      expect(repository.stepProgressStates.single.startedAt, clock.value);
+    },
+  );
+
   testWidgets('la séquence passe au deuxième passage si répétitions > 1', (
     tester,
   ) async {
@@ -1460,6 +1537,7 @@ String _sessionSnapshot({
   ScoreInputMode scoreInputMode = ScoreInputMode.manual,
   List<String> imageMediaIds = const [],
   List<Map<String, Object?>> exerciseSteps = const [],
+  bool autoStartNextTimedStep = true,
   String? videoMediaId,
 }) {
   return jsonEncode({
@@ -1490,6 +1568,7 @@ String _sessionSnapshot({
               'exerciseVideoMediaIdSnapshot': videoMediaId,
               'videoMediaIdSnapshot': videoMediaId,
               'exerciseStepsSnapshot': exerciseSteps,
+              'autoStartNextTimedStepSnapshot': autoStartNextTimedStep,
             },
           ],
         }),