Feature Request: Add multi-language UI support (i18n), starting with Chinese (中文)

Feature Request

Description

Claude Code currently only has an English interface. As a Chinese-speaking user, I'd love to see built-in multi-language support (i18n) for the CLI interface, starting with Simplified Chinese (简体中文).

What should be localized

• All CLI prompts and messages (e.g., "Allow", "Deny", "Esc to cancel", status messages)
• Help text (/help, command descriptions)
• Error messages and warnings
• Settings/configuration labels
• Slash command descriptions

Suggested approach

1. Add a language or locale setting in ~/.claude/settings.json (e.g., "locale": "zh-CN")
2. Use an i18n framework or simple key-value locale files
3. Start with English (default) and Chinese, then expand to other languages

Why this matters

• Claude Code is increasingly popular among Chinese-speaking developers
• A localized interface significantly lowers the barrier to entry
• Many developers are more comfortable working in their native language
• This would make Claude Code more accessible globally

Current workaround

Using ~/.claude/CLAUDE.md with instructions like "请始终使用中文回复" can make Claude respond in Chinese, but the CLI interface itself (menus, prompts, status text) remains in English.

Environment

• Claude Code on macOS (also applies to Linux/Windows)
• Terminal: iTerm2 / Terminal.app with full CJK support