[BUG] IME (ATOK) candidate window overlaps input area on Windows Terminal

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When typing Japanese text using ATOK IME in Claude Code's input prompt,
the IME candidate/conversion window overlaps with the input area,
making it difficult to see what is being typed.

What Should Happen?

The IME candidate window should appear directly above or below the
input cursor without overlapping the input text, as it does in
normal terminal input (outside of Claude Code's TUI).

Error Messages/Logs

Steps to Reproduce

1. Launch Claude Code in Windows Terminal on Windows 11
2. Switch to ATOK (Japanese IME)
3. Type Japanese text requiring conversion (e.g. "かんきょう" → "環境")
4. Observe the position of the IME candidate window

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.191 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

• Windows 11 26H2 (Build 26300)
• Windows Terminal 1.24.11321.0
• IME: ATOK (JustSystems)
• The same issue likely occurs with MS-IME and Google Japanese Input,

as the root cause appears to be Claude Code's TUI (React Ink) hiding
the real terminal cursor position from the OS IME subsystem.

• Related issues: #1547, #25186, #19207, #35307

<img width="1423" height="354" alt="Image" src="https://github.com/user-attachments/assets/cba0f327-a656-4b2e-a032-eb6ba9e60732" />