Japanese Text Input: End Key Navigation Broken for Multibyte Characters

Question

**Bug Description**

On lines containing multibyte characters, the End key no longer moves the caret to the end of the line. This used to work before. I suspect the caret movement destination is now based on character count instead of byte count.

**Environment Info**
- Platform: darwin
- Terminal: tmux
- Version: 1.0.30
- Feedback ID: 990d8370-5f3b-4deb-a2bd-dbc501e84dfd

**Errors**
```json
[]
```