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.App/Rendering/GameWindow.cs

@@ -300,6 +300,12 @@ public sealed class GameWindow : IDisposable
     private static readonly bool DevToolsEnabled =
         Environment.GetEnvironmentVariable("ACDREAM_DEVTOOLS") == "1";
 
+    // Phase I.3 — real ICommandBus for live sessions. Constructed when
+    // the live session spins up (so SendChatCmd handlers can close over
+    // _liveSession + Chat). Null when offline; PanelContext then falls
+    // back to NullCommandBus.Instance.
+    private AcDream.UI.Abstractions.LiveCommandBus? _commandBus;
+
     // Phase G.1-G.2 world lighting/time state.
     public readonly AcDream.Core.World.WorldTimeService WorldTime =
         new AcDream.Core.World.WorldTimeService(
@@ -1221,6 +1227,41 @@ public sealed class GameWindow : IDisposable
                     senderGuid: speech.SenderGuid,
                     isRanged: speech.IsRanged);
 
+            // Phase I.3: real ICommandBus. Panels publish SendChatCmd here
+            // and we route it to the right wire opcode (Talk / Tell / ChatChannel)
+            // plus a local echo into ChatLog so the player sees their own
+            // message immediately. Closes over _liveSession + Chat so this
+            // wiring only exists for the lifetime of the live session.
+            var liveSession = _liveSession;
+            var chat = Chat;
+            _commandBus = new AcDream.UI.Abstractions.LiveCommandBus();
+            _commandBus.Register<AcDream.UI.Abstractions.SendChatCmd>(cmd =>
+            {
+                if (string.IsNullOrEmpty(cmd.Text)) return;
+                switch (cmd.Channel)
+                {
+                    case AcDream.UI.Abstractions.ChatChannelKind.Say:
+                        liveSession.SendTalk(cmd.Text);
+                        chat.OnSelfSent(AcDream.Core.Chat.ChatKind.LocalSpeech, cmd.Text);
+                        break;
+                    case AcDream.UI.Abstractions.ChatChannelKind.Tell:
+                        if (string.IsNullOrEmpty(cmd.TargetName)) return;
+                        liveSession.SendTell(cmd.TargetName, cmd.Text);
+                        chat.OnSelfSent(
+                            AcDream.Core.Chat.ChatKind.Tell, cmd.Text,
+                            targetOrChannel: cmd.TargetName);
+                        break;
+                    default:
+                        var resolved = AcDream.UI.Abstractions.ChannelResolver.Resolve(cmd.Channel);
+                        if (resolved is null) return;
+                        liveSession.SendChannel(resolved.Value.ChannelId, cmd.Text);
+                        chat.OnSelfSent(
+                            AcDream.Core.Chat.ChatKind.Channel, cmd.Text,
+                            targetOrChannel: resolved.Value.DisplayName);
+                        break;
+                }
+            });
+
             // Issue #5: feed PrivateUpdateVital + PrivateUpdateVitalCurrent
             // into LocalPlayer so VitalsPanel can draw Stam / Mana bars.
             _liveSession.VitalUpdated += v =>
@@ -4116,9 +4157,15 @@ public sealed class GameWindow : IDisposable
         // today) would need manual protection.
         if (DevToolsEnabled && _imguiBootstrap is not null && _panelHost is not null)
         {
+            // Phase I.3 — prefer the live command bus when a live session
+            // is up so panel-emitted SendChatCmd actually flows server-ward.
+            // Fall back to NullCommandBus for offline / pre-connect renders.
+            AcDream.UI.Abstractions.ICommandBus bus =
+                _commandBus ?? (AcDream.UI.Abstractions.ICommandBus)
+                    AcDream.UI.Abstractions.NullCommandBus.Instance;
             var ctx = new AcDream.UI.Abstractions.PanelContext(
                 (float)deltaSeconds,
-                AcDream.UI.Abstractions.NullCommandBus.Instance);
+                bus);
             _panelHost.RenderAll(ctx);
             _imguiBootstrap.Render();
         }