feat(ui+net): #16 LiveCommandBus + WorldSession.Send{Talk,Tell,Channel} + SendChatCmd wiring

Replaces NullCommandBus.Instance in PanelContext with a real
LiveCommandBus when a live session is active. Panels publish
SendChatCmd; the host routes it to the right wire opcode + emits
a ChatLog.OnSelfSent local echo (optimistic; retail-equivalent
for Talk).

Pieces:
- ChatChannelKind enum (UI.Abstractions) - mirrors holtburger's
  ChatChannelKind (references/holtburger/.../client/types.rs:35-49).
- SendChatCmd record (UI.Abstractions) - (Channel, TargetName?, Text).
- LiveCommandBus (UI.Abstractions) - single-handler-per-type;
  Register<T> throws on double-register; Publish<T> logs missing
  handler but does not throw.
- ChannelResolver (UI.Abstractions) - port of holtburger's
  resolve_legacy_channel (client/commands.rs:50-62) mapping
  ChatChannelKind to legacy ChatChannel ids verbatim from
  holtburger-protocol/.../chat/types.rs:8-24 (Fellow=0x0800,
  AllegianceBroadcast=0x02000000, Vassals=0x1000, Patron=0x2000,
  Monarch=0x4000, CoVassals=0x01000000).
- WorldSession.SendTalk / SendTell / SendChannel - 3-line wrappers
  around existing ChatRequests.Build* + SendGameAction. Internal
  GameActionCapture seam + InternalsVisibleTo for tests.
- GameWindow registers SendChatCmd handler: Say -> SendTalk +
  ChatLog echo, Tell -> SendTell + echo, channel kinds ->
  ChannelResolver.Resolve -> SendChannel + echo.

12 new tests across SendChatCmd + LiveCommandBus + ChannelResolver
+ WorldSessionChat. NullCommandBus.Instance retained for back-compat
when no live session.

Solution total: 893 green (51 + 229 + 613).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Net.Tests/WorldSessionChatTests.cs

@@ -0,0 +1,79 @@
+using System.Net;
+using AcDream.Core.Net;
+using AcDream.Core.Net.Messages;
+
+namespace AcDream.Core.Net.Tests;
+
+/// <summary>
+/// Phase I.3 — verifies that <see cref="WorldSession.SendTalk"/>,
+/// <see cref="WorldSession.SendTell"/>, and <see cref="WorldSession.SendChannel"/>
+/// produce the same wire bytes that <see cref="ChatRequests"/> builders do,
+/// using a sequence number drawn from <see cref="WorldSession.NextGameActionSequence"/>.
+///
+/// <para>
+/// Uses the internal <c>GameActionCapture</c> test seam to intercept the
+/// game-action body before it hits the (unseeded) ISAAC-encrypted wire path.
+/// </para>
+/// </summary>
+public sealed class WorldSessionChatTests
+{
+    private static WorldSession NewSession()
+    {
+        // Bind to a throwaway loopback endpoint; we never actually
+        // exchange packets — the capture hook intercepts the body.
+        var ep = new IPEndPoint(IPAddress.Loopback, 65000);
+        return new WorldSession(ep);
+    }
+
+    [Fact]
+    public void SendTalk_EmitsBytesIdenticalToChatRequestsBuildTalk()
+    {
+        using var session = NewSession();
+        byte[]? captured = null;
+        session.GameActionCapture = body => captured = body;
+
+        session.SendTalk("hello");
+
+        // After SendTalk, the sequence counter has been incremented to 1.
+        // ChatRequests.BuildTalk(seq=1, "hello") should match exactly.
+        byte[] expected = ChatRequests.BuildTalk(1, "hello");
+        Assert.NotNull(captured);
+        Assert.Equal(expected, captured);
+    }
+
+    [Fact]
+    public void SendTell_EmitsBytesIdenticalToChatRequestsBuildTell()
+    {
+        using var session = NewSession();
+        byte[]? captured = null;
+        session.GameActionCapture = body => captured = body;
+
+        session.SendTell("Alice", "hey");
+
+        byte[] expected = ChatRequests.BuildTell(1, "Alice", "hey");
+        Assert.NotNull(captured);
+        Assert.Equal(expected, captured);
+    }
+
+    [Fact]
+    public void SendChannel_IncrementsSequence_AndMatchesBuildChatChannel()
+    {
+        using var session = NewSession();
+        var captured = new System.Collections.Generic.List<byte[]>();
+        session.GameActionCapture = body => captured.Add(body);
+
+        session.SendChannel(channelId: 0x00000800u, "raid plan");
+        session.SendChannel(channelId: 0x02000000u, "allegiance ping");
+
+        Assert.Equal(2, captured.Count);
+        Assert.Equal(ChatRequests.BuildChatChannel(1, 0x00000800u, "raid plan"),     captured[0]);
+        Assert.Equal(ChatRequests.BuildChatChannel(2, 0x02000000u, "allegiance ping"), captured[1]);
+    }
+
+    [Fact]
+    public void SendTalk_NullText_Throws()
+    {
+        using var session = NewSession();
+        Assert.Throws<ArgumentNullException>(() => session.SendTalk(null!));
+    }
+}