Bug: TextField corrupts Korean IME composition on customer-account surface

When a buyer types Korean using their OS’s IME inside a <TextField> rendered by a customer-account.* UI extension, characters are duplicated and pre-commit composition state leaks into the field.

The same input typed into a native HTML <textarea> on the same browser, same OS, same IME comes through cleanly. Two distinct defect patterns are visible — see Defect patterns below.

This almost certainly affects all CJK IMEs (Japanese hiragana/katakana, Chinese Pinyin/Bopomofo) since they all rely on the same browser-level compositionstart / compositionupdate / compositionend event sequence. We have only confirmed Korean so far because that is what our merchant reported.

Repro steps

  1. Open the extension in a customer-account context.

  2. Switch the OS keyboard to Korean (2-set / 두벌식) IME.

  3. Type the following sentence at a normal pace, with one space between words. Do not paste — typing through the IME is the trigger.

    안녕하세요 좋은 제품입니다 테스트 리뷰입니다 (“Hello, it’s a good product. Test review.”)

    For reference, the keystroke sequence in 2-set Hangul is: dkssudgktpdy whgdms wpvnadlqslek xptmxm flqbdlqslek

Expected

안녕하세요 좋은 제품입니다 테스트 리뷰입니다

Actual (in the customer-account <TextField>)

안녕하세세요요 좋은 제푸품입니다다 테스스트트 리뷰뷰이입니다다