Thai language rendering issue - combining characters (vowels/tones) not displayed correctly

Description

Thai language text is not rendered correctly when using Claude Code. Combining characters (vowels like ์ิ ์ี ์ึ ์ื and tone marks ์่ ์้ ์๊ ์๋) are missing or displayed incorrectly.

Environment

• OS: macOS (Darwin 25.2.0)
• Terminal: Terminal.app and iTerm2 (both have the same issue)
• Claude Code version: Latest
• Locale: LANG=en_US.UTF-8, LC_ALL=en_US.UTF-8

Steps to Reproduce

1. Open terminal (Terminal.app or iTerm2 on macOS)
2. Confirm Thai text displays correctly in the terminal before launching Claude Code
3. Run claude to start Claude Code
4. Type or receive Thai text with combining characters (e.g., "สวัสดี", "ภาษาไทย")
5. Observe that vowels and tone marks are missing or incorrectly positioned

Expected Behavior

Thai text should display correctly with all combining characters properly positioned.

Actual Behavior

• Thai combining characters (vowels and tone marks) are not displayed correctly
• Text appears incomplete or garbled
• This issue does NOT occur in the terminal before entering Claude Code

Additional Context

This appears to be related to the terminal UI library (possibly Ink) not correctly handling Thai combining characters.