Start-of-line navigation is weird in new REPL, with completions showing #126851

In Python 3.13, if you're on a REPL line with completions showing above, typing Home or Ctrl+a will move the cursor to be in front of the first completion result, instead of to the start of the line being edited (or, to put it another way, immediately after the input prompt) where it "should" be.

Input otherwise works normally. If you start typing, the completions will disappear and the characters will go to the beginning of the input line. But it's disconcerting to see the cursor placed so far from where it "should" be.

Originally posted by @ferdnyc in #118878 (comment)