[combobox] An example for Custom value to be rendered inside Combobox

### Support needed
Input inside trigger example, something like React Select.

## Use Case
I want to use Combobox to build a component where consumers can render custom content as the selected value (e.g., a person's avatar with their name, product images with titles, etc.). This is similar to how React Select allows custom `SingleValue` components.

Currently, the default examples in the docs don't address this use case for single-select scenarios.

## Current Challenge
When trying to implement this pattern, I'm running into architectural issues with how to structure the trigger and input elements:

### Approach 1: Input inside Trigger (causes event conflicts)
```jsx

{/* Input clicks bubble to trigger, causing open/close flickering */}

```

### Approach 2: Multiple separate triggers (workaround)
```jsx

### Expected behavior:
- No selection: Show input with placeholder, clicking anywhere opens popup
- With selection: Show custom selected value, clicking anywhere opens popup and focuses input
- While typing: Hide selected value, show input for filtering
- The input does not retain the value of the selected item.

### Questions for the Team

- What's the recommended pattern for implementing custom selected value displays with React select like behavior?