Feature Request: /insights report language localization (i18n support)

Summary

The /insights command generates an excellent usage analysis report, but currently the report content is hardcoded in English only. For non-English speaking users, it would be very helpful to support localization — at minimum, respecting the user's language preference configured in CLAUDE.md or system locale.

Current Behavior

• /insights always generates the HTML report in English
• The CLAUDE.md language instructions (e.g., "use Simplified Chinese for all output") are not respected by the insights report generation
• All section titles, descriptions, analysis text, and suggestions are in English

Expected Behavior

The /insights report should support localization, possible approaches:

1. Respect CLAUDE.md language settings — if a user has configured a preferred language, generate the report in that language
2. Add a --lang flag — e.g., /insights --lang zh-CN to specify the output language
3. Detect system locale — auto-detect from the OS locale setting

Use Case

I work on a medical health platform monorepo with a Chinese-speaking team. All our documentation, commit messages, and Claude interactions are in Simplified Chinese. The insights report being English-only creates friction when sharing with team members.

Environment

• Claude Code CLI on Windows 10
• Model: claude-opus-4-6
• Language preference: Simplified Chinese (configured in global CLAUDE.md)