[BUG] /settings: language change in slash command is not persisted (Enter does not save)

Description

Changing the language via the /settings slash command does not save the new value. After selecting a different language and pressing Enter, the change is not persisted — reopening /settings shows the previous value.

Steps to reproduce

1. Run /settings in an interactive Claude Code session.
2. Navigate to the language option.
3. Change the value to a different language.
4. Press Enter to confirm.
5. Close /settings and reopen it (or restart the session).

Expected behavior

The selected language is saved and reflected on next open of /settings and in subsequent sessions.

Actual behavior

The change is not saved. Pressing Enter does not persist the new value; the setting reverts to the previous one.

Environment

• Claude Code version: 2.1.128
• Platform: macOS (Darwin 25.4.0)
• Shell: zsh

Notes

Other settings should be checked to see if this is specific to the language field or a broader persistence issue with /settings.