feat: add message management and delivery states

src/main/chat-server.ts

@@ -10,6 +10,7 @@ export interface ChatServerEvents {
   message: (from: DeviceInfo, msg: MessageEnvelope) => void
   recall: (from: DeviceInfo, messageId: string) => void
   typing: (from: DeviceInfo) => void
+  read: (from: DeviceInfo, upToMessageId: string) => void
 }
 
 export class ChatServer extends EventEmitter {
@@ -77,6 +78,10 @@ export class ChatServer extends EventEmitter {
         case 'recall':
           if (peer) this.emit('recall', peer, frame.messageId)
           break
+        case 'read':
+          // 已读回执: 接收方已看到 upTo (含), 把 ≤ upTo 的发送方消息视为已读
+          if (peer) this.emit('read', peer, frame.upTo)
+          break
         case 'typing':
           if (peer) this.emit('typing', peer)
           break