feat(net+chat): #19 TurbineChat (0xF7DE) codec + ChatChannelInfo + SetTurbineChatChannels parser

Full port of holtburger's TurbineChat sidecar wire path:

- TurbineChat.cs: 0xF7DE codec with three payload variants
  (EventSendToRoom S->C, RequestSendToRoomById C->S, Response).
  10-field outer header (size_first/blob_type/dispatch_type/
  target_type/target_id/transport_type/transport_id/cookie/
  size_second + payload).
- UTF-16LE turbine string codec with 1-or-2 byte variable-length
  prefix (high bit on first byte signals 2-byte form). Mirrors
  holtburger's read_turbine_string / write_turbine_string at
  references/holtburger/.../messages/chat/turbine.rs:502-544.
- SetTurbineChatChannels.cs: 0x0295 GameEvent sub-opcode parser
  (10 x u32 channel ids). Wired through GameEventDispatcher in
  WorldSession ctor; routes to GameEventWiring + TurbineChatState.
- ChatChannelInfo.cs (Core): unified record union with Legacy
  (channel id + name) and Turbine (room id + chat type +
  dispatch type + name) variants, plus IsSelfEchoChannel
  predicate (Tells = false, channels = true so optimistic echo
  is suppressed where the server will echo).
- TurbineChatState.cs (Core): Enabled flag + 10 cached room ids
  + NextContextId() cookie counter starting at 1.
- WorldSession adds TurbineChatReceived + TurbineChannelsReceived
  events; SendTurbineChatTo outbound builds RequestSendToRoomById
  + sends through SendGameAction. ProcessDatagram dispatches
  0xF7DE at the top level.
- GameWindow constructs TurbineChatState, subscribes inbound
  EventSendToRoom -> ChatLog.OnChannelBroadcast; extends I.3's
  SendChatCmd handler to route Turbine kinds (General/Trade/Lfg/
  Roleplay/Society/Olthoi) through TurbineChat first, fall back
  to legacy ChatChannel send when state.Enabled == false.

Round-trip golden fixtures from holtburger source verified for
all three payload variants + UTF-16LE strings (short + long
prefix + non-ASCII Cafe + empty) + SetTurbineChatChannels.

26 new tests:
- TurbineChatTests, SetTurbineChatChannelsTests in Core.Net.Tests
- ChatChannelInfoTests, TurbineChatStateTests in Core.Tests

Solution total: 960 green (243 Core.Net + 625 Core + 92 UI).

ACE doesn't run a TurbineChat server, so codec is "ready when
needed" for retail-server-emulating setups. Legacy ChatChannel
fallback continues to work for current ACE-against-acdream play.

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

src/AcDream.Core.Net/GameEventWiring.cs

@@ -36,7 +36,8 @@ public static class GameEventWiring
         CombatState combat,
         Spellbook spellbook,
         ChatLog chat,
-        LocalPlayerState? localPlayer = null)
+        LocalPlayerState? localPlayer = null,
+        TurbineChatState? turbineChat = null)
     {
         ArgumentNullException.ThrowIfNull(dispatcher);
         ArgumentNullException.ThrowIfNull(items);
@@ -66,6 +67,34 @@ public static class GameEventWiring
             if (s is not null) chat.OnPopup(s);
         });
 
+        // ── TurbineChat channel list (0x0295 SetTurbineChatChannels) ─────
+        // Phase I.6: arrives once at login (and after chat-server reconnect)
+        // listing the per-session room ids assigned to General / Trade /
+        // LFG / Roleplay / Society / Olthoi (and the optional Allegiance
+        // Turbine room). Without this the TurbineChat outbound path stays
+        // disabled and the chat panel falls back to the legacy ChatChannel
+        // GameAction. See holtburger client/messages.rs:220-223 for the
+        // server-message handling pattern.
+        if (turbineChat is not null)
+        {
+            dispatcher.Register(GameEventType.SetTurbineChatChannels, e =>
+            {
+                var p = SetTurbineChatChannels.TryParse(e.Payload.Span);
+                if (p is null) return;
+                turbineChat.OnChannelsReceived(
+                    allegianceRoom:           p.Value.AllegianceRoom,
+                    generalRoom:              p.Value.GeneralRoom,
+                    tradeRoom:                p.Value.TradeRoom,
+                    lfgRoom:                  p.Value.LfgRoom,
+                    roleplayRoom:             p.Value.RoleplayRoom,
+                    olthoiRoom:               p.Value.OlthoiRoom,
+                    societyRoom:              p.Value.SocietyRoom,
+                    societyCelestialHandRoom: p.Value.SocietyCelestialHandRoom,
+                    societyEldrytchWebRoom:   p.Value.SocietyEldrytchWebRoom,
+                    societyRadiantBloodRoom:  p.Value.SocietyRadiantBloodRoom);
+            });
+        }
+
         // ── Errors ───────────────────────────────────────────────
         // Phase I.5: WeenieError + WeenieErrorWithString parsers existed
         // (GameEvents.ParseWeenieError(WithString)) but were never registered.