feat(ipc): mirror TypingIpc provider slots under ChatTwo namespace (v1.4.9 R4)

HellionChat replaces ChatTwo (conflict detection prevents parallel loading)
but third-party plugins with a no-fork policy keep subscribing only to the
ChatTwo.*-prefixed IPC gates. Mirroring the two TypingIpc provider slots
under the ChatTwo namespace lets those plugins keep working without code
changes on their side.

Mirrored slots:
- ChatTwo.GetChatInputState  ←→ HellionChat.GetChatInputState
- ChatTwo.ChatInputStateChanged ←→ HellionChat.ChatInputStateChanged

Implementation:
- Two additional ICallGateProvider fields (ChatTwoStateQueryGate +
  ChatTwoStateChangedGate) with the identical ChatInputState tuple
  signature. The tuple's underlying types match ChatTwo's surface byte-
  for-byte (bool/bool/bool/bool/int/ushort — ChatType is `ushort` in both
  repos), so Dalamud's IPC marshalling matches across plugin boundaries
  even when the subscribing plugin defines its own copy of the ChatType
  enum.
- ctor registers the new provider gates and binds RegisterFunc(GetState)
  to ChatTwoStateQueryGate so query calls route to the same backing path.
- Update() pushes the state to both ChatTwoStateChangedGate and the
  existing StateChangedGate in lockstep.
- Dispose() unregisters both query gates.

Ipc/ExtraChat.cs is intentionally unchanged — it is a subscriber on
ExtraChat's own IPC, not a provider, so no compatibility mirror applies.

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

HellionChat/Ipc/TypingIpc.cs

@@ -19,6 +19,17 @@ internal sealed class TypingIpc : IDisposable
     private ICallGateProvider<ChatInputState> StateQueryGate { get; }
     private ICallGateProvider<ChatInputState, object?> StateChangedGate { get; }
 
+    // v1.4.9 R4: ChatTwo IPC compatibility mirror. Some third-party plugins
+    // have a no-fork policy and subscribe only to ChatTwo.*-prefixed IPC
+    // gates. HellionChat replaces ChatTwo (conflict detection prevents
+    // parallel loading), so mirroring the ChatTwo provider slots lets those
+    // plugins keep working without code changes on their side. The tuple
+    // shape is textually identical to ChatTwo's IPC surface (same member
+    // order, same underlying types — ChatType is `ushort` in both repos)
+    // so Dalamud's IPC marshalling matches across plugin boundaries.
+    private ICallGateProvider<ChatInputState> ChatTwoStateQueryGate { get; }
+    private ICallGateProvider<ChatInputState, object?> ChatTwoStateChangedGate { get; }
+
     private ChatInputState LastState;
     private bool HasState;
 
@@ -33,7 +44,16 @@ internal sealed class TypingIpc : IDisposable
             "HellionChat.ChatInputStateChanged"
         );
 
+        // v1.4.9 R4: ChatTwo-prefixed compatibility slots (see class-level comment).
+        ChatTwoStateQueryGate = Plugin.Interface.GetIpcProvider<ChatInputState>(
+            "ChatTwo.GetChatInputState"
+        );
+        ChatTwoStateChangedGate = Plugin.Interface.GetIpcProvider<ChatInputState, object?>(
+            "ChatTwo.ChatInputStateChanged"
+        );
+
         StateQueryGate.RegisterFunc(GetState);
+        ChatTwoStateQueryGate.RegisterFunc(GetState);
     }
 
     private ChatInputState BuildState()
@@ -67,10 +87,13 @@ internal sealed class TypingIpc : IDisposable
         HasState = true;
         LastState = state;
         StateChangedGate.SendMessage(state);
+        // v1.4.9 R4: mirror on ChatTwo-prefixed slot for no-fork-policy plugins.
+        ChatTwoStateChangedGate.SendMessage(state);
     }
 
     public void Dispose()
     {
         StateQueryGate.UnregisterFunc();
+        ChatTwoStateQueryGate.UnregisterFunc();
     }
 }