Thai text rendering issue - characters overlapping in input field

Description

Thai text renders incorrectly in the Claude Code CLI input field. Characters appear overlapped/stacked, making it difficult to type and read Thai text.

Environment

• Claude Code version: 2.1.25
• OS: WSL2 (Linux 6.6.87.2-microsoft-standard-WSL2) on Windows
• Terminal: Windows Terminal
• Shell: bash/zsh

Steps to Reproduce

1. Open Claude Code CLI in WSL terminal
2. Type Thai text, e.g., ทดสอบพิมพ์ภาษาไทย
3. Observe that characters overlap/stack incorrectly

Expected Behavior

Thai text should render correctly with proper spacing, similar to how it appears in the regular WSL terminal.

Actual Behavior

Thai combining characters (vowels and tone marks like ั ิ ี ่ ้) overlap with base consonants, making text unreadable. The cursor position also appears incorrect.

Additional Context

• Regular WSL terminal displays Thai text correctly
• The issue occurs both when typing directly and when copy/pasting Thai text
• This appears to be related to how the CLI calculates string width for Thai combining characters