[bug] opencode produces gabled text when input containing non-ascii characters

[Peng-YM]

When input contains Chinese characters, opencode often converts them into garbled text.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Bug [Visual]: TUI populated with gibberish upon copying #2256: TUI populated with gibberish upon copying - reports similar text display corruption issues in the terminal UI
• The terminal UI display is abnormal #1146: The terminal UI display is abnormal - shows display problems with special characters and terminal rendering
• [bug] display Issues of Double Underscores in TUI #392: Display issues of Double Underscores in TUI - demonstrates character rendering problems where text appears garbled in the interface

Feel free to ignore if none of these address your specific case.