New theme is too dark/high-contrast — please restore ability to choose previous (lighter) theme

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

Claude Code Version: 1.49585.0 (41ad1d)
Platform: macOS
Claude Desktop

A recent update changed the default theme to a much darker, higher-contrast look
(black background, white text). The previous theme was noticeably softer/lighter
and easier on the eyes for extended use.

The new theme causes eye strain during long working sessions, especially in
low-light environments or for users sensitive to high contrast.

There doesn't appear to be a way to switch back to the previous theme, or to
choose a lighter/softer color scheme instead.

### What Should Happen?

Users should be able to choose between multiple themes, including the previous
lighter/softer theme that was available before this change — either via a
theme selector in settings, or by restoring the old default as an option.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

1. Update Claude Desktop to the latest version (1.49585.0).
2. Open the app and check Settings for theme options.
3. Observe: the theme is now dark background / high contrast (black + white text),
and there is no option to switch to the previous, lighter theme.

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

1.49585.0

### Platform

Other

### Operating System

macOS

### Terminal/Shell

Other

### Additional Information

_No response_

The issue names Claude Desktop settings but no files, tests, or entry points. Start by locating the theme and settings implementation for macOS, then determine how the previous lighter theme can be exposed or restored. Done means users can select a lighter, softer theme and the choice is reflected when the app is reopened.

索引モデルが issue の本文から書いたものです。