macOS: Support RTL Tabbing when using tabs style


## Expected Behavior

The tab bar should correctly mirror its layout when the system is in RTL mode, consistent with how native macOS apps (e.g. Terminal.app, Safari) handle RTL tab bars.

## Config

```
macos-titlebar-style = tabs
```

## Current Behavior

https://github.com/user-attachments/assets/a36b1a3c-a7f6-44c4-b95e-5584d82c27b9