[Bug]: Installer uses Simplified Chinese instead of the macOS system language

### Description

During the OpenCLI app installation, the interface was displayed in Simplified Chinese even though my MacBook's system language is set to English.

I did not select Chinese during setup. The installer should detect and use the device's preferred language, or fall back to English if the locale cannot be determined.
Although i want to be clear, i clicked the first two "continue" buttons without knowing what was going on, i only translated the last setup screen to English via chatgpt.

### Steps to Reproduce

1. Set the macOS system language to English.
2. Install the OpenCLI app on the Mac.
3. Proceed through the installation flow.
4. Observe that the installation interface is displayed in Simplified Chinese instead of English.

### Expected Behavior

The installer should use the operating system's preferred language. In this case, it should display English because the MacBook's system language is English.

If automatic language detection fails, OpenCLI should fall back to English or present a clearly visible language selector.

### OpenCLI Version

0.1.36 (after app installation)

### Node.js Version

22.x

### Operating System

macOS

### Logs / Screenshots

```shell
Environment:
- macOS 26.5
- macOS system language: English
- Language displayed by the installer: Simplified Chinese
- Node.js: v22.23.1

No error message was shown. `opencli --version` was unavailable because OpenCLIApp was not running.
```

No files, tests, or entry points are named. Reproduce the installation flow on macOS with English as the system language, then locate the installer's language initialization and locale detection; done means the interface follows the system language or visibly falls back to English when detection fails.

Written by the indexing model from the issue text.