[Bug/Regression] Arrow key navigation skips multi-line prompt navigation

Bug Description
The up/down button used to let me navigate multiple lines in a prompt, then fallback to start of line if no further lines above, then fallback further to previous messages navigation. It now just moves straight to messages navigation.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.158
• Feedback ID: 762cee42-b325-4a52-83d2-92f32966f4d1

Errors

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