pyrepl loses input and mis-positions cursor when F2 is pressed

Bug report

Bug description:

This is bad for 2 different reasons:

1. pyrepl loses track of the cursor, thinking it's in the first column when it's actually in the middle of the screen somewhere, so future screen drawing operations have unexpected results
2. on top of that, anything you were in the middle of typing when you pressed F2 is discarded, so if you wanted to access the history to copy something out and paste it into the command you're writing, oops, it's gone

CPython versions tested on:

3.13

Operating systems tested on:

Linux

在 Linux 上使用 CPython 3.13 重现 pyrepl 中 F2 的行为，然后跟踪 F2 的处理过程和屏幕重绘路径。当当前输入得到保留、光标保持正确位置且后续屏幕绘制正常运行时，即视为完成。