Circular avatar with image or initials fallback.

```jsx
<Avatar size={32}><AvatarImage src="/me.png" alt="Zach" /></Avatar>
<Avatar size={32}><AvatarFallback>ZK</AvatarFallback></Avatar>
```

With no children it renders the neutral gradient disc used in the console header. Sizes: 24 in dense rows, 32 in headers, 40+ on profile screens.