[Chrome, Android] The Hangul composition breaks on the first character when the placeholder is visible

Description

Hangul is the Korean alphabet.

When using a Korean IME with Chrome on Android, the first character does not compose correctly. Instead of combining consonant and vowel inputs into a single syllable, they are inserted as separate characters.

Recording

https://github.com/user-attachments/assets/0372fb29-b6fa-4497-9e5c-51e7768a104b

Sandbox

Reproducible on the official Plain Text example: https://www.slatejs.org/examples/plaintext

Steps

1. Clear all content from the editor.
2. Using a Korean IME, enter the characters in the following order:
   • "ㅇ" → "ㅏ" → "ㅇ" → "ㅏ"
3. Ensure that the first "ㅇ" and "ㅏ" do not composed into "아" and remain as separate characters.

Expectation

The characters “ㅇ” and “ㅏ” are composed into “아”

Environment

• Slate Version: 0.120.0
• Operating System: Android 15
• Browser: Chrome

Context

This issue seems to be related to placeholder rendering with IME composition.