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>

src/AcDream.UI.Abstractions/LiveCommandBus.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+
+namespace AcDream.UI.Abstractions;
+
+/// <summary>
+/// Real <see cref="ICommandBus"/> implementation — single-handler-per-type
+/// dispatch keyed by <c>typeof(T)</c>. Replaces <see cref="NullCommandBus"/>
+/// in live sessions; <see cref="NullCommandBus"/> persists for tests and
+/// non-live UI scenarios where no command flow is wanted.
+///
+/// <para>
+/// <b>Threading.</b> Both <see cref="Register{T}"/> and <see cref="Publish{T}"/>
+/// run on the render thread today (panels render on the render thread, and
+/// host wiring happens at startup). The internal handler dictionary is
+/// not synchronized — register all handlers during host setup before the
+/// panel host starts rendering.
+/// </para>
+///
+/// <para>
+/// Phase I.3 of the chat/UI consolidation plan
+/// (<c>~/.claude/plans/ticklish-conjuring-cake.md</c>): primary client of
+/// the bus is the <see cref="SendChatCmd"/> handler wired by GameWindow
+/// against <c>WorldSession.SendTalk/SendTell/SendChannel</c> + the local
+/// <c>ChatLog</c> echo.
+/// </para>
+/// </summary>
+public sealed class LiveCommandBus : ICommandBus
+{
+    private readonly Dictionary<Type, Delegate> _handlers = new();
+
+    /// <summary>
+    /// Register a single handler for commands of type <typeparamref name="T"/>.
+    /// Throws <see cref="InvalidOperationException"/> if a handler is already
+    /// registered for this type — single-handler-per-type is intentional so
+    /// command routing is unambiguous.
+    /// </summary>
+    public void Register<T>(Action<T> handler) where T : notnull
+    {
+        ArgumentNullException.ThrowIfNull(handler);
+        if (_handlers.ContainsKey(typeof(T)))
+            throw new InvalidOperationException(
+                $"A handler for command type {typeof(T).FullName} is already registered.");
+        _handlers[typeof(T)] = handler;
+    }
+
+    /// <inheritdoc />
+    public void Publish<T>(T command) where T : notnull
+    {
+        ArgumentNullException.ThrowIfNull(command);
+        if (_handlers.TryGetValue(typeof(T), out var handler))
+        {
+            ((Action<T>)handler).Invoke(command);
+        }
+        else
+        {
+            // Soft-warn: command published with no registered handler.
+            // Don't throw — the host may publish optional commands a non-
+            // live build doesn't wire (e.g. inventory pre-Phase I.7).
+            Console.WriteLine(
+                $"[LiveCommandBus] no handler registered for {typeof(T).FullName}; dropping.");
+        }
+    }
+}