feat(sidebar): improve folder link accessibility and UX (#10349)
### Description
```Refering the Discussion```: [#10328](https://github.com/vercel/turborepo/discussions/10328)
This PR improves the accessibility and user experience of the sidebar folder links by separating the navigation and toggle functionality into distinct interactive elements.
**Key Changes:**
- Separated the folder link and toggle button into distinct elements for clearer interaction patterns
- Added proper `aria-label` attributes for screen readers to indicate expand/collapse actions
- Improved visual feedback with hover states on the toggle button
### Testing Instructions
This is what it was earlier:
https://drive.google.com/file/d/1-XLu9N_nAoksvfLQQlQQndniZFstABaM/view?usp=sharing
And this is how it looks now:
https://drive.google.com/file/d/1YOqaRRn6L-cFq2cgZH5Lg7u5HSx-d6A9/view?usp=sharing
1. **Basic Functionality**
- Navigate to any page with a sidebar containing folder links
2. **Accessibility Testing**
- Use a screen reader to navigate the sidebar
4. **Edge Cases**
- Test with long folder names to ensure proper text truncation
- Verify behavior when a folder is both active and collapsed
