feat(ui): écran Exécution de séance

Ajoute l'écran d'exécution de séance (presentation/workout_execution_screen.dart),
avec les ajustements application/domaine/repositories nécessaires et la
navigation depuis l'accueil et l'écran séance-modèle. flutter analyze
propre, 15/15 tests verts, build APK debug validé.

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

lib/application/use_cases.dart

@@ -590,6 +590,8 @@ final class ActiveWorkoutSessionUseCases {
   final IdGenerator ids;
   final String originDeviceId;
 
+  Future<ActiveWorkoutSession?> findOpen() => sessionRepository.findOpen();
+
   Future<ActiveWorkoutSession> startFromTemplate(String templateId) async {
     final template = await templateRepository.findById(templateId);
     if (template == null) {
@@ -659,6 +661,97 @@ final class ActiveWorkoutSessionUseCases {
     return result;
   }
 
+  Future<ActiveSetResult> recordCurrentSetResult({
+    required String sessionId,
+    required String programSnapshotId,
+    required String exerciseSnapshotId,
+    required int programIndex,
+    required int exerciseIndex,
+    required int setIndex,
+    int? actualTimeMs,
+    int? actualReps,
+    double? actualScore,
+    String? scoreLabelSnapshot,
+    String? scoreUnitSnapshot,
+  }) async {
+    final now = clock.now();
+    final result = ActiveSetResult(
+      metadata: _newMetadata(ids, originDeviceId, now),
+      activeWorkoutSessionId: sessionId,
+      programSnapshotId: programSnapshotId,
+      exerciseSnapshotId: exerciseSnapshotId,
+      programIndex: programIndex,
+      exerciseIndex: exerciseIndex,
+      setIndex: setIndex,
+      completedAt: now,
+      actualTimeMs: actualTimeMs,
+      actualReps: actualReps,
+      actualScore: actualScore,
+      scoreLabelSnapshot: scoreLabelSnapshot,
+      scoreUnitSnapshot: scoreUnitSnapshot,
+    );
+    await sessionRepository.saveSetResult(result);
+    return result;
+  }
+
+  Future<ActiveWorkoutSession> updateProgress({
+    required String sessionId,
+    required int programIndex,
+    required int exerciseIndex,
+    required int setIndex,
+  }) async {
+    final session = await _requiredSession(sessionId);
+    final updated = session.copyWith(
+      currentProgramIndex: programIndex,
+      currentExerciseIndex: exerciseIndex,
+      currentSetIndex: setIndex,
+      metadata: session.metadata.touch(clock.now()),
+    );
+    await sessionRepository.save(updated);
+    return updated;
+  }
+
+  Future<ActiveWorkoutSession> quitAndSave(String sessionId) async {
+    final session = await _requiredSession(sessionId);
+    final now = clock.now();
+    final saved = session.copyWith(
+      status: ActiveWorkoutStatus.savedExit,
+      lastPersistedAt: now,
+      elapsedActiveMs: session.elapsedActiveMillisecondsAt(now),
+      metadata: session.metadata.touch(now),
+    );
+    await sessionRepository.save(saved);
+    return saved;
+  }
+
+  Future<ActiveWorkoutSession> abandon(String sessionId) async {
+    final session = await _requiredSession(sessionId);
+    final now = clock.now();
+    final abandoned = session.copyWith(
+      status: ActiveWorkoutStatus.abandoned,
+      endedAt: now,
+      lastPersistedAt: now,
+      elapsedActiveMs: session.elapsedActiveMillisecondsAt(now),
+      metadata: session.metadata.touch(now),
+    );
+    await sessionRepository.save(abandoned);
+    return abandoned;
+  }
+
+  Future<ActiveWorkoutSession> complete(String sessionId) async {
+    final session = await _requiredSession(sessionId);
+    final now = clock.now();
+    final completed = session.copyWith(
+      status: ActiveWorkoutStatus.completed,
+      endedAt: now,
+      lastPersistedAt: now,
+      elapsedActiveMs: session.elapsedActiveMillisecondsAt(now),
+      metadata: session.metadata.touch(now),
+    );
+    await sessionRepository.save(completed);
+    return completed;
+  }
+
   Future<ActiveRestState> startRestAfterSet({
     required String sessionId,
     required int afterProgramIndex,