CLI looks wrong in xterm with non-UTF charset inside

[UnitedMarsupials]

Describe the bug

My $LANG is set to uk_UA.KOI8-U -- and the fonts I'm using with xterm have the matching encoding (koi8-u). Copilot uses wrong symbols for the pseudo-graphics making the screen rather hard to use. Worse, some character-combinations emitted by the program seem to confuse xterm requiring me to reset it.

Affected version

unknown (cli-0.0.394)

Steps to reproduce the behavior

The below instructions use Ukrainian as example, but any non-ASCII and non-UTF LANG-setting would demonstrate the same behavior.

1. If you don't already have Cyrillic fonts installed -- the xlsfonts -fn '*fixed*koi8-*' prints nothing -- install fonts with koi8-u encoding, such as these.
2. Launch xterm using one of such fonts: xterm -fn '-gemini-fixed-medium-r-normal--20-200-75-75-c-100-koi8-u'.
3. Set LANG environment variable inside the xterm to uk_UA.KOI8-U.
4. Start copilot.

Expected behavior

Expecting lines to be drawn as lines, not as sequences of Cyrillic "Б" (see attached snapshot).

Additional context