feat(ios): align chat library memory and tasks with web

ios/Sources/LiveKit/VoiceSession.swift

@@ -112,6 +112,9 @@ final class VoiceSession: ObservableObject {
         NotificationCenter.default.removeObserver(self)
     }
 
+    /// Identity bound to Talk, independent of the current Chats selection.
+    var boundConversationID: String? { tokenClient.conversationID }
+
     /// Explicit chat-to-Talk navigation tears down the prior room first.
     func bindConversation(_ id: String?) async {
         await disconnect()