Use std::optional instead of sentinel values for absent data

src/balancing/ArenaSimulation.h

@@ -58,7 +58,7 @@ struct ArenaStatus
 
     TeamStatus teams[2];
     bool finished = false;
-    int winnerTeam = -1;  // 0 or 1 when finished; -1 while running
+    std::optional<int> winnerTeam;  // 0 or 1 when finished; nullopt while running
     // Game time the fight has lasted (simulated ticks * fixed tick duration).
     // Meaningful once finished; the battle duration shown for completed runs.
     double durationSeconds = 0.0;
@@ -80,7 +80,7 @@ public:
 
     ArenaStatus getStatus() const;
     bool isFinished() const;
-    int getWinnerTeam() const;
+    std::optional<int> getWinnerTeam() const;
     Tick getCurrentTick() const;
 
     const ArenaConfig& getArenaConfig() const;
@@ -122,7 +122,7 @@ private:
     entt::entity m_team2HqEntity;
 
     bool m_finished;
-    int m_winnerTeam;
+    std::optional<int> m_winnerTeam;
     std::atomic<bool> m_stopRequested;
 
     // Static accumulated threat per team, computed once from the configured roster.