test(engine-ambient): cover BattleRecoveryInfo setter ambient write-through

Setter is the asymmetric one (write-through inside scope, unlike ViewerId's
no-op-in-scope) — adding parity with the SetRealTimeNetworkBattle ambient
setter test to catch future regressions if the routing branch is touched.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

SVSim.BattleEngine.Tests/BattleAmbientTests.cs

@@ -189,4 +189,15 @@ public class BattleAmbientTests
         using var _ = BattleAmbient.Enter(ctx);
         Assert.That(Wizard.Data.BattleRecoveryInfo, Is.SameAs(info));
     }
+
+    [Test]
+    public void BattleRecoveryInfo_SetInsideScope_WritesAmbient()
+    {
+        var ctx = new BattleAmbientContext();
+        using var _ = BattleAmbient.Enter(ctx);
+        var info = (Wizard.BattleRecoveryInfo)System.Runtime.Serialization
+            .FormatterServices.GetUninitializedObject(typeof(Wizard.BattleRecoveryInfo));
+        Wizard.Data.BattleRecoveryInfo = info;
+        Assert.That(ctx.RecoveryInfo, Is.SameAs(info));
+    }
 }