Linebreak bug when typing in Korean.

### Expected
Linebreak should work properly when typing in Korean.

### Observed
When a line break occurs during typing, the next line appears to be filled with identical characters, and it seems like no further input is being accepted. Specifically, when text wraps to a new line, that entire new line gets filled with duplicate characters and becomes unresponsive to additional typing.

### Reproduced
1. Keep typing in Korean until the end of a line.
2. Do not break the line with enter, but continue writing.
3. The observed phenomenon occurs

https://github.com/user-attachments/assets/9b673f38-ff59-4a04-ad20-fe5f5d45b846

### Where did you see the bug

- OS: macOS
- OS version: Sonoma 14.3
- Browser (if applicable): Chrome
- Browser version (if applicable): 134.0.6998.89 (ARM64)
- Simplenote app version: 2.23.2 beta 1

Strangely, this does not happen in Safari.

Start by reproducing the issue in the Simplenote app on macOS with Chrome and Korean input, following the listed steps. Compare the behavior with Safari and confirm that wrapping no longer duplicates characters or prevents further typing; the issue names no source file or test to begin with.

Written by the indexing model from the issue text.