[FEATURE] Option to configure language for auto-generated session history titles

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Session history titles are auto-generated in English regardless of the user's language. For non-English users (e.g., Japanese users), all session titles appear in English even when the conversation is conducted entirely in another language. This makes it difficult to quickly identify sessions at a glance.

Proposed Solution

Add a setting (e.g., in Claude Code settings or settings.json) to configure the preferred language for auto-generated session history titles. When set, titles should be generated in the specified language regardless of the interface language.

Example: "sessionTitleLanguage": "ja" would generate titles in Japanese.

Alternative Solutions

Currently, starting conversations in the target language sometimes influences the title language, but this is inconsistent and not reliable. There is no way to guarantee titles appear in a specific language.

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

1. User is a Japanese speaker who uses Claude Code entirely in Japanese.
2. 2. All session history titles appear in English (e.g., "Build random Pokemon display website").
3. 3. The user wants titles to appear in Japanese (e.g., "ランダムポケモン表示サイト構築") for easier navigation.
4. 4. With this feature, setting "sessionTitleLanguage": "ja" in settings.json would automatically generate Japanese titles.

Additional Context

_No response_