[Bug] IME composition events not handled in CLI input on Windows (Vietnamese, CJK languages)

Bug Description
Bug: Cannot type Vietnamese (and likely other IME-based languages) in Claude Code CLI on Windows

Environment:

Claude Code v2.1.97
Windows 11 Pro (Build 10.0.26200.8037)
Terminal: Windows Terminal with UTF-8 (chcp 65001)
Unicode UTF-8 system locale enabled
Vietnamese IME: Unikey/EVKey (Telex/VNI input method)
Description:
When typing Vietnamese characters with diacritics (e.g., "tiếng Việt") in the Claude Code CLI input prompt, characters are dropped or lost during composition. The IME composing process (where multiple keystrokes combine into one accented character) conflicts with the CLI's input handler.

For example, typing "tiếng" using Telex method (t-i-e-61-n-g) results in missing or garbled characters.

Steps to reproduce:

Open Windows Terminal with UTF-8 code page (chcp 65001)
Launch claude
Try typing Vietnamese text with any IME (Unikey, EVKey, GoTiengViet)
Characters are lost/dropped during diacritic composition
Expected: Vietnamese text with diacritics should appear correctly.

Actual: Characters are dropped or missing when composing diacritics.

Workaround: Copy-paste pre-typed text works, but direct typing does not.

Note: This likely affects all languages that use IME-based input (Chinese, Japanese, Korean, Vietnamese). The issue seems to be in the terminal UI input handler (ink/React-based) not properly handling IME composition events.

Environment Info

• Platform: win32
• Terminal: null
• Version: 2.1.97
• Feedback ID: c6bd0e9e-3f1f-4a67-b9e4-6c757c634d50

Errors

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