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 重現 pyrepl 中 F2 的行為，然後追蹤 F2 的處理流程和螢幕重繪路徑。當目前的輸入獲得保留、游標保持正確位置，且後續螢幕繪製正常運作時，即視為完成。