Incorrect cursor position and duplicate input glitch when typing Korean/English on signs

When typing or editing text on signs using the mobile touch keyboard (especially when switching between Korean and English or editing multi-line text), the input focus and cursor position become offset. As a result, characters are inserted in wrong positions or duplicated.

Steps to Reproduce:

1. Place a sign and open the text input interface.

2. Type text in Korean (or switch between Korean IME and English keyboard).

3. Attempt to add a second line or backspace/edit existing text.

4. Notice that new characters appear in wrong lines or existing letters duplicate/overlap incorrectly.

Expected Result:

Text should be typed and edited smoothly according to the cursor position on the sign.

Observed Result:

The cursor/text index breaks, causing letters to split, shift to wrong lines, or repeat unexpectedly.