test(battle-engine M13): HeadlessNetworkBattleMgr constructs headless (construction probe)

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

SVSim.BattleEngine.Tests/HeadlessFixture.cs

@@ -202,6 +202,19 @@ namespace SVSim.BattleEngine.Tests
             var dm = GameMgr.GetIns().GetDataMgr();
             SetField(dm, "_playerCharaId", HeadlessMasterData.PlayerCharaId);
             SetField(dm, "_enemyCharaId", HeadlessMasterData.EnemyCharaId);
+            // NetworkBattleManagerBase.CreateBackgroundId() (M13) reads
+            // GameMgr.GetIns().GetNetworkUserInfoData().GetFieldId() when the RecoveryManager yields no
+            // bg id (NullRecoveryManager.BackGroundId == -1). In production RealTimeNetworkAgent seeds
+            // this NetworkUserInfoData at match start; the bare construction path leaves GameMgr's
+            // _netUser null (no lazy init, unlike the other GodObject getters). Seed a no-op instance
+            // whose _selfInfo carries just "fieldId" (GetFieldId reads _selfInfo["fieldId"]); field id 1
+            // == ForestField, a valid background. Nothing here drives game state — it only satisfies the
+            // network mgr's background lookup so a single-battle-only SingleBattleMgr never needs.
+            var netUser = new NetworkUserInfoData();
+            netUser.SetSelfInfo(
+                new System.Collections.Generic.Dictionary<string, object> { ["fieldId"] = 1 },
+                isWatchReplayRecovery: false);
+            GameMgr.GetIns().SetNetworkUserInfoData(netUser);
             _done = true;
         }