写一个实时分享终端的工具

### 初衷/目标

xxx

```shell
$ sharetty
# 监听端口 http://localhost:3000, 等待有人用浏览器打开
# 连接之后打开新的终端，输入命令，与浏览器同步输出
```

### TODO类型

- [ ] 类库
- [ ] 框架
- [ ] 服务
- [x] 命令行工具

### 预计时间

- [ ] 一天
- [x] 一周
- [ ] 两周
- [ ] 一月
- [ ] 更久

### 相关链接

[https://github.com/axetroy/todo](https://github.com/axetroy/todo)

Start with the proposed `sharetty` command flow and review the related todo link for context; no source files, tests, or entry points are identified in the issue. Clarify the terminal-to-browser connection and synchronization requirements before implementation, with completion meaning that a browser can connect and observe synchronized terminal input and output.

Written by the indexing model from the issue text.