🐛 Borders displayed too long in environment with East Asian Ambiguous Width == 2

[aoyama-val]

A lot of CJK environments assume that East Asian Ambiguous Width characters are double width, whereas Eastern enviroments single. In former, the borders are displayed with double width and wrapped.It would be preferrable if there was an option to treat those characters as double width or to use ASCII characters to draw borders.

To reproduce:

• Use a terminal that is configurable so that Ambiguous Width characters are double width (e.g. iTerm2)