Session titles should respect CLAUDE.md language settings (e.g. Japanese)

Feature Request

When CLAUDE.md specifies a language preference (e.g., Japanese), auto-generated session titles in the sidebar should be generated in that language instead of defaulting to English.

Current Behavior

• Session titles are always auto-generated in English, regardless of CLAUDE.md language settings or the language of the conversation.
• Users who work primarily in non-English languages need to manually /rename every session to make the sidebar readable.

Expected Behavior

• If CLAUDE.md contains a language directive (e.g., "応答内容は日本語で記載すること" / "Respond in Japanese"), auto-generated session titles should follow that language.
• Alternatively, a dedicated setting like sessionTitleLanguage in settings.json would also work.

Use Case

I use Claude Code entirely in Japanese. Every new session generates an English title, and I have to manually rename it with /rename each time. This is a small but persistent friction point, especially when managing many sessions.

Related Issues

• #35799 (closed as duplicate, but the underlying feature was not implemented)

Environment

• Claude Code CLI + Desktop App (macOS)
• CLAUDE.md with explicit Japanese language directive