test(free-battle): /finish echoes battle_result with no rank fields

SVSim.UnitTests/Controllers/FreeBattleControllerTests.cs

@@ -112,4 +112,30 @@ public class FreeBattleControllerTests
             "Missing deck → RC_BATTLE_MATCHING_ILLEGAL.");
         Assert.That(data.GetProperty("node_server_url").GetString(), Is.EqualTo(""));
     }
+
+    [Test]
+    public async Task Finish_emits_battle_result_echo_and_four_field_minimum()
+    {
+        await using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync();
+        var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsJsonAsync("/unlimited_free_battle/finish", FinishBody(battleResult: 1));
+
+        Assert.That(resp.IsSuccessStatusCode, Is.True);
+        var raw = await resp.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(raw);
+        var data = doc.RootElement;
+        Assert.That(data.GetProperty("battle_result").GetInt32(), Is.EqualTo(1));
+        Assert.That(data.GetProperty("get_class_experience").GetInt32(), Is.EqualTo(0));
+        Assert.That(data.GetProperty("class_experience").GetInt32(), Is.EqualTo(0));
+        Assert.That(data.GetProperty("class_level").GetInt32(), Is.EqualTo(1));
+
+        // Strict subset — no rank fields. The client doesn't read them on free-battle
+        // finish; emitting them would be wire-format pollution.
+        Assert.That(raw, Does.Not.Contain("\"rank\""));
+        Assert.That(raw, Does.Not.Contain("\"after_battle_point\""));
+        Assert.That(raw, Does.Not.Contain("\"after_master_point\""));
+        Assert.That(raw, Does.Not.Contain("\"successive_win"));
+    }
 }