核心概念

SMeetingEngine        会议业务：账号、会议 CRUD、会控、等候室、子会议、录制、签到
   └── srtc: SRTCEngine   媒体：频道连接、采集、发布、订阅、渲染

const meeting: SMeetingEngine = new SMeetingEngine(LogLevel.info);

登录        login(token)              ← token 由业务后端签发
   ↓
会议管理    createRoom / attendeeRoom / detailRoom …   （不在会中也能调）
   ↓
入会        enterRoom({ nickname, meetingId | roomNo })
   ↓
会中        requestOpenMic / subscribeRemoteVideoTrack / admin* / …
   ↓
离会        exitRoom()
   ↓
登出        logout() → dispose()

// 直接用 SRTC
const mic = srtc.createLocalMicTrack(preset);
await mic.startCapture();
await channel.publishLocalAudioTrack(mic);

// 用 SMeeting
await meeting.requestOpenMic();

ForEach(this.users, (u: MeetingUserInfo) => {
  SMeetingRemoteVideoView({ meeting: this.meeting, uid: u.uid })
    .width('50%').height(160)
}, (u: MeetingUserInfo) => u.uid)

await meeting.subscribeRemoteVideoTrack(uid);
const track: Track | undefined = meeting.getRemoteVideoTrack(uid);

const mcu = await meeting.subscribeRemoteVideoMcu(uid);
await meeting.unsubscribeRemoteVideoMcu();

meeting.delegates.add(delegate);