/config language setting does not persist — always reverts to 'default english'

Bug Description

When changing the language setting to "Korean" via the /config dialog, the setting does not persist. Upon reopening /config, the language always shows "default english" again.

Steps to Reproduce

1. Run /config in Claude Code CLI
2. Change language setting from "default english" to "Korean"
3. Close the config dialog
4. Run /config again
5. Language setting has reverted back to "default english"

Expected Behavior

The language setting should persist across sessions after being changed via /config.

Actual Behavior

The language setting always reverts to "default english". Checking ~/.claude/settings.json and ~/.claude/settings.local.json shows no language field is being saved.

Environment

• OS: macOS (Darwin 25.3.0)
• Claude Code: Latest version
• Shell: zsh

Workaround

Using CLAUDE.md project instructions to enforce language preference works as expected. Only the /config UI setting fails to persist.