fix(net): conform character entry and session shutdown

tests/AcDream.Core.Net.Tests/Messages/CharacterEnterWorldTests.cs

@@ -1,4 +1,5 @@
 using System.Buffers.Binary;
+using AcDream.Core.Net;
 using AcDream.Core.Net.Messages;
 using AcDream.Core.Net.Packets;
 
@@ -41,6 +42,67 @@ public class CharacterEnterWorldTests
         Assert.Equal(0, body[pos++]);
         Assert.Equal(4 + 4 + 16, body.Length);  // opcode + guid + padded string
     }
+
+    [Fact]
+    public void SessionSelection_UsesCanonicalCharacterListAccountInF657()
+    {
+        CharacterList.Parsed characters = MakeCharacters(
+            [new CharacterList.Character(0x50000001u, "Ready", 0)],
+            accountName: "CanonicalCase");
+
+        WorldSession.EnterWorldSelection selection =
+            WorldSession.SelectCharacterForEnterWorld(characters, 0);
+
+        ReadOnlySpan<byte> body = selection.EnterWorldBody;
+        Assert.Equal(CharacterEnterWorld.EnterWorldOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body));
+        Assert.Equal(0x50000001u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body[4..]));
+        ushort length = BinaryPrimitives.ReadUInt16LittleEndian(body[8..]);
+        Assert.Equal("CanonicalCase",
+            System.Text.Encoding.ASCII.GetString(body.Slice(10, length)));
+    }
+
+    [Theory]
+    [InlineData(0u, 0u)]
+    [InlineData(0x50000001u, 1u)]
+    [InlineData(0x50000001u, 30u)]
+    public void SessionSelection_RejectsUnavailableActiveIdentity(
+        uint guid,
+        uint secondsGreyedOut)
+    {
+        CharacterList.Parsed characters = MakeCharacters(
+            [new CharacterList.Character(guid, "Unavailable", secondsGreyedOut)],
+            accountName: "Account");
+
+        Assert.Throws<InvalidOperationException>(() =>
+            WorldSession.SelectCharacterForEnterWorld(characters, 0));
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(1)]
+    public void SessionSelection_RejectsIndexOutsideActiveCollection(int index)
+    {
+        CharacterList.Parsed characters = MakeCharacters(
+            [new CharacterList.Character(0x50000001u, "Ready", 0)],
+            accountName: "Account");
+
+        Assert.Throws<ArgumentOutOfRangeException>(() =>
+            WorldSession.SelectCharacterForEnterWorld(characters, index));
+    }
+
+    private static CharacterList.Parsed MakeCharacters(
+        IReadOnlyList<CharacterList.Character> active,
+        string accountName) =>
+        new(
+            Status: 0,
+            Characters: active,
+            DeletedCharacters: [],
+            SlotCount: 11,
+            AccountName: accountName,
+            UseTurbineChat: true,
+            HasThroneOfDestiny: true);
 }
 
 public class GameMessageFragmentTests