Open Radar

 
**Description:**
When a view controller is embedded as a child in a container view controller, the focus system fails to properly traverse the `preferredFocusEnvironments` tree. The container view controller needs to explicitly pass through its wrapped child environment by overriding `preferredFocusEnvironments` to return its children.

**Steps to Reproduce:**
1. Let's say `MyViewController` customizes the focus behavior its sub views (e.g. to reverse the focus order of a group of buttons) and this works as expected
2. If this view controller is now embedded in a container view controller, `WrapperViewController`, the customization logic (which lives in the overriden property `preferredFocusEnvironments` of `MyViewController`) is never called
3. The solution is to also override `preferredFocusEnvironments` in the container view controller:

```
class WrapperViewController: UIViewController {
    open override var preferredFocusEnvironments: [any UIFocusEnvironment] {
        return self.children // children contains a MyViewController instance
    }
}
```

**Expected Results:**
- Focus behavior should be consistent whether `MyViewController` is or is not a child view controller
- Focus should follow the custom order defined in `preferredFocusEnvironments`

**Actual Results:**
- When MyViewController is not a child: `preferredFocusEnvironments` is called in MyViewController
- When MyViewController is child: Focus system falls back to visual search order, ignoring MyViewController's `preferredFocusEnvironments` override
- The fix requires explicitly overriding `preferredFocusEnvironments` in the container to return its children

**Additional Info:**
- Xcode 16.2 (16C5032a)