fix(guild): friend_list returns bare array-at-root (matches GuildFriendListTask.Parse)

GuildFriendListTask.Parse() reads base.ResponseData[data][i] directly —
data must be a bare JSON array, not {friends:[...]}.  Delete the
GuildFriendListResponse wrapper DTO; promote GuildInviteCandidateDto to its
own file.  Controller now returns List<GuildInviteCandidateDto> so the
middleware wraps it as data:[…].  Update wire-shape and integration tests to
assert array-at-root.

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

SVSim.EmulatedEntrypoint/Models/Dtos/Guild/GuildInviteCandidateDto.cs

@@ -0,0 +1,41 @@
+using MessagePack;
+using System.Text.Json.Serialization;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Guild;
+
+/// <summary>
+/// One entry in the /guild/friend_list response.
+/// GuildFriendListTask.Parse() iterates base.ResponseData["data"][i] directly — data is a
+/// bare JSON array, not a wrapper object. This DTO is the element type of that array.
+/// </summary>
+[MessagePackObject]
+public class GuildInviteCandidateDto
+{
+    [JsonPropertyName("viewer_id"), Key("viewer_id"), JsonConverter(typeof(SVSim.EmulatedEntrypoint.Models.Dtos.Common.StringifiedLongConverter))]
+    public long ViewerId { get; set; }
+
+    [JsonPropertyName("name"), Key("name")]
+    public string Name { get; set; } = "";
+
+    [JsonPropertyName("emblem_id"), Key("emblem_id"), JsonConverter(typeof(SVSim.EmulatedEntrypoint.Models.Dtos.Common.StringifiedLongConverter))]
+    public long EmblemId { get; set; }
+
+    [JsonPropertyName("country_code"), Key("country_code")]
+    public string CountryCode { get; set; } = "";
+
+    [JsonPropertyName("rank"), Key("rank"), JsonConverter(typeof(SVSim.EmulatedEntrypoint.Models.Dtos.Common.StringifiedIntConverter))]
+    public int Rank { get; set; }
+
+    [JsonPropertyName("degree_id"), Key("degree_id"), JsonConverter(typeof(SVSim.EmulatedEntrypoint.Models.Dtos.Common.StringifiedIntConverter))]
+    public int DegreeId { get; set; }
+
+    [JsonPropertyName("is_friend"), Key("is_friend")]
+    public int? IsFriend { get; set; }
+
+    [JsonPropertyName("is_friend_apply"), Key("is_friend_apply")]
+    public int? IsFriendApply { get; set; }
+
+    /// <summary>true => friend is already in a guild and can't be invited.</summary>
+    [JsonPropertyName("is_join_guild"), Key("is_join_guild")]
+    public bool IsJoinGuild { get; set; }
+}