feat(net): Campaign LA LA7a — CharacterDelete/CharacterRestore/CharacterError wire messages

Ports the three character-management wire messages LA7 (design spec §7,
plan §11 item 4) identified as missing before the character-select
screen (LA8) can be built: delete, restore, and the server error channel.
Message types + tests only — no WorldSession/Runtime/UI wiring, that is
LA7b.

CharacterDelete (0xF655): outbound account+SLOT-INDEX request per
Proto_UI::SendDeleteCharacter@0x00546b30 (retail packs the account as
String16L then writes the trailing u32 directly after — NOT the character
guid; CPlayerSystem::DeleteCharacter@0x0055f830 resolves that slot via
CharacterSet::GetSlot before sending). The server's ack reuses the same
opcode with an empty body (ACE GameMessageCharacterDelete.cs); a fresh
CharacterList follows separately per CharacterHandler.cs:322 — that
refresh flow is explicitly out of scope here (LA7b).

CharacterRestore (0xF7D9 request / 0xF643 response): guid-only request,
per ACE (CharacterHandler.cs:331-385, ReadUInt32 only) and holtburger
(CharacterRestoreRequestData, guid-only) independent consensus. The
decompiled call site (Proto_UI::SendAdminRestoreCharacter@0x00546cf0)
appears to pack two extra strings, but its only caller
(CPlayerSystem::RestoreCharacter@0x0055d760) passes an uninitialized
local (`class PStringBase<char>* edx;`, never assigned) as the second
argument and `this` (a CPlayerSystem*, not a string) as the third —
textbook decompiler register-corruption, not real arguments. No
divergence-register row: this follows the correct reading of a corrupted
decompile, not a deviation from retail (spec §11 item 4). The response
reuses opcode 0xF643, a genuine retail collision with
CharacterCreateResponse (ACE's own comment: "This is a duplicate...",
GameMessageOpcode.cs:42); GameMessageCharacterRestore.cs always writes a
success shape (flag=1 + guid + name + secondsGreyedOut), but retail's
CharacterRestore handler can also reply via the CharacterCreateResponse
path on failure (e.g. NameInUse) with a flag-only body and no trailing
fields — the parser mirrors that conditionality instead of assuming the
four fields are always present.

CharacterError (0xF659): u32 error code, confirmed directly from retail's
inbound dispatcher UIQueueManager::ProcessNetBlobData@0x0055b000 ->
CPlayerSystem::Handle_CharacterError@0x0055d5d0, which reads
`enum charError` straight off the wire. The Code enum is a verbatim port
of retail's own enum charError (docs/research/named-retail/acclient.h:
4038-4067, 26 members incl. CHAR_ERROR_NUM_ERRORS) rather than a subset
filtered through ACE — retail's header names four members ACE's C#
CharacterError enum omits (LoggedOn, NoPremade, AccountInUse,
CharacterIsBooted) because ACE's server never sends them, though a
genuine retail server could. The 32-bit storage-width compiler sentinel
FORCE_charError_32_BIT is deliberately excluded (not a real value).
Unknown codes never throw — RawErrorCode always preserves the wire value.
Today acdream cannot surface any character-stage server error; this is
the first parser for the family.

46 new tests (byte-exact builder assertions, ACE-serializer-shaped
parser fixtures via the existing AceWireWriter test helper, all 26
retail error codes round-tripped, unknown/truncated/wrong-opcode
handling). Full Core.Net.Tests suite: 951 passed, 0 failed, 0 skipped.
Release build green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

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

@@ -0,0 +1,83 @@
+using System.Buffers.Binary;
+using AcDream.Core.Net.Messages;
+
+namespace AcDream.Core.Net.Tests.Messages;
+
+public sealed class CharacterDeleteTests
+{
+    [Fact]
+    public void BuildRequestBody_Layout_OpcodeThenAccountThenSlot()
+    {
+        byte[] body = CharacterDelete.BuildRequestBody("testaccount", characterSlot: 3);
+
+        int pos = 0;
+        Assert.Equal(CharacterDelete.Opcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(pos))); pos += 4;
+
+        // String16L("testaccount") = u16(11) + 11 ASCII bytes, padded to a
+        // 4-byte boundary counted from the length prefix: 2 + 11 = 13 -> 16
+        // (3 pad bytes).
+        ushort len = BinaryPrimitives.ReadUInt16LittleEndian(body.AsSpan(pos));
+        Assert.Equal(11, len); pos += 2;
+        string name = System.Text.Encoding.ASCII.GetString(body.AsSpan(pos, 11));
+        Assert.Equal("testaccount", name); pos += 11;
+        Assert.Equal(0, body[pos++]);
+        Assert.Equal(0, body[pos++]);
+        Assert.Equal(0, body[pos++]);
+
+        uint slot = BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(pos)); pos += 4;
+        Assert.Equal(3u, slot);
+
+        Assert.Equal(4 + 16 + 4, body.Length);  // opcode + padded string + slot
+        Assert.Equal(pos, body.Length);
+    }
+
+    [Fact]
+    public void BuildRequestBody_ExactByteSequence_ShortAccount()
+    {
+        // "ab" -> String16L = u16(2) + 2 bytes = 4, already 4-byte aligned,
+        // no padding.
+        byte[] body = CharacterDelete.BuildRequestBody("ab", characterSlot: 0x11u);
+
+        byte[] expected =
+        [
+            0x55, 0xF6, 0x00, 0x00,  // opcode 0xF655 LE
+            0x02, 0x00,              // String16L length = 2
+            (byte)'a', (byte)'b',    // string bytes
+            0x11, 0x00, 0x00, 0x00,  // characterSlot = 0x11 LE
+        ];
+
+        Assert.Equal(expected, body);
+    }
+
+    [Fact]
+    public void BuildRequestBody_NullAccountName_Throws()
+    {
+        Assert.Throws<ArgumentNullException>(
+            () => CharacterDelete.BuildRequestBody(null!, characterSlot: 0));
+    }
+
+    [Fact]
+    public void IsAcknowledgement_AcceptsOpcodeOnlyBody()
+    {
+        byte[] body = BitConverter.GetBytes(CharacterDelete.Opcode);
+
+        Assert.True(CharacterDelete.IsAcknowledgement(body));
+    }
+
+    [Fact]
+    public void IsAcknowledgement_RejectsRequestShapedBody()
+    {
+        byte[] request = CharacterDelete.BuildRequestBody("acct", characterSlot: 1);
+
+        Assert.False(CharacterDelete.IsAcknowledgement(request));
+    }
+
+    [Fact]
+    public void IsAcknowledgement_RejectsTruncatedOrDifferentOpcode()
+    {
+        Assert.False(CharacterDelete.IsAcknowledgement([0x55, 0xF6, 0x00]));
+        Assert.False(CharacterDelete.IsAcknowledgement(BitConverter.GetBytes(0xF656u)));
+        Assert.False(CharacterDelete.IsAcknowledgement([]));
+    }
+}