Multiple lines in prompt

Lines 2,4, and 8 are entered one line above the bottom, hiding the first line with the "|USER|" field. Moreover, when the prompt reaches the maximum height, the program crashes.

Reproduce the issue in Neovim by entering a multiline prompt, including one at maximum height, and observe the misplaced lines and crash. Inspect the prompt rendering and height-handling entry points; done means all lines remain visible, the USER field is not obscured, and maximum-height prompts do not crash.

Written by the indexing model from the issue text.