fix(guild): /guild/update response — flat detail under guild (matches GuildUpdateTask.Parse)

GuildUpdateTask.Parse() reads data[guild] as GuildDetailInfo directly; the previous
GuildDetailSubTree wrapper (data[guild][detail]) caused json[guild_id].ToInt() to
crash on the client. Split GuildUpdateResponse (flat) from GuildUpdateEmblemResponse
(nested, correct for GuildEmblemUpdateTask.Parse). Also surfaces guild_name from the
request through UpdateGuildRequest.Name -> service -> repo so the client rename is honoured.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.UnitTests/Wire/GuildWireShape.cs

@@ -1,5 +1,6 @@
 using NUnit.Framework;
 using System.Text.Json;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Common.Guild;
 using SVSim.EmulatedEntrypoint.Models.Dtos.Guild;
 
 namespace SVSim.UnitTests.Wire;
@@ -35,6 +36,55 @@ public class GuildWireShape
         Assert.That(first.GetProperty("emblem_id").GetString(), Is.EqualTo("100000001"));
     }
 
+    private static GuildDetailDto SampleDetail => new()
+    {
+        GuildId = 100_000_001,
+        GuildName = "X",
+        LeaderName = "L",
+        LeaderViewerId = 7,
+        Activity = 1,
+        JoinCondition = 1,
+        MemberNum = 1,
+        GuildEmblemId = 100_000_000L,
+        Description = "",
+    };
+
+    [Test]
+    public void GuildUpdate_response_serializes_with_flat_guild_detail()
+    {
+        // GuildUpdateTask.Parse() reads data["guild"] as GuildDetailInfo directly — no "detail" wrapper.
+        var resp = new GuildUpdateResponse { Guild = SampleDetail };
+        var json = JsonSerializer.Serialize(resp, Opts);
+        using var doc = JsonDocument.Parse(json);
+        var guild = doc.RootElement.GetProperty("guild");
+
+        // guild_id must be DIRECTLY under "guild"
+        Assert.That(guild.TryGetProperty("guild_id", out var gid), Is.True, "guild_id must be directly under guild");
+        Assert.That(gid.GetString(), Is.EqualTo("100000001"));
+
+        // No nested "detail" wrapper
+        Assert.That(guild.TryGetProperty("detail", out _), Is.False, "no detail wrapper for /guild/update");
+    }
+
+    [Test]
+    public void GuildUpdateEmblem_response_serializes_with_nested_detail()
+    {
+        // GuildEmblemUpdateTask.Parse() reads data["guild"]["detail"] — wrapper is required.
+        var resp = new GuildUpdateEmblemResponse
+        {
+            Guild = new GuildDetailSubTree { Detail = SampleDetail }
+        };
+        var json = JsonSerializer.Serialize(resp, Opts);
+        using var doc = JsonDocument.Parse(json);
+        var guildNode = doc.RootElement.GetProperty("guild");
+
+        Assert.That(guildNode.TryGetProperty("detail", out var detail), Is.True, "detail wrapper must exist for /guild/update_emblem");
+        Assert.That(detail.GetProperty("guild_id").GetString(), Is.EqualTo("100000001"));
+
+        // guild_id must NOT be directly under "guild"
+        Assert.That(guildNode.TryGetProperty("guild_id", out _), Is.False, "guild_id must be inside detail, not at guild level");
+    }
+
     [Test]
     public void GuildInfo_non_joined_serializes_to_prod_shape()
     {