Korean (Hangul) characters display as broken/garbled in input field #3493

Bug Description

When typing Korean (Hangul) characters in the OpenCode interface input field, the characters appear as broken/garbled text, making it impossible to verify typed content in real-time.

Steps to Reproduce

1. Launch OpenCode
2. Try typing Korean text in the input field (e.g., 안녕하세요)
3. Observe that the characters appear broken/garbled

Expected Behavior

Korean characters should display correctly in the input field as they are being typed.

Actual Behavior

Korean characters appear as broken/garbled characters or empty boxes, preventing users from seeing what they are typing.

Environment

• OS: macOS 26.0.1 (Build 25A362)
• OpenCode Version: 0.15.18
• Terminal: xterm-256color
• Locale: ko_KR.UTF-8

Additional Context

• The AI correctly recognizes and processes Korean input (backend works fine)
• The issue is purely visual/UI rendering related
• After sending the message, AI responds correctly in Korean
• The problem only affects real-time input visibility, not functionality

Impact

This makes it extremely difficult for Korean users to:

• Verify spelling while typing
• Catch typos before sending
• Use OpenCode effectively in Korean

Suggested Fix

Possible solutions:

• Add CJK (Chinese, Japanese, Korean) font support to the input field
• Ensure proper UTF-8 rendering in the UI component
• Test with fonts that include Korean glyphs (e.g., Noto Sans CJK, D2Coding)