[bug]切换配色方案到none时，无法使用快捷键ctrl+l去清屏

[luoyunhe]

version: 2.3.1
system: windows 11

[kingToolbox]

Duplicate of #335

In the new WindTerm_2.4.0_Prerelease_1, a new dumb system has been added. In addition to features such as highlighting and folding, the dumb system supports clearing the screen locally. So for some dumb devices, especially serial devices, if you need to clear the screen locally, please use dumb system instead of none system.

The dumb system also supports -> command prompt for the VxWorks system. Please download and use it, if you have any questions, please let me know, thank you.

BTW:
Please use dumb system with caution and only for the dumb devices. If the remote supports the clear screen command, using dumb system to clear the screen locally will cause the local display to be out of sync with the remote, which may cause various display errors.