DevIndex: Disable controls toggle button on learn route #9312
Description
When starting DevIndex directly on the /learn route, clicking the 'hamburger' controls toggle button causes a JS error because the home view (where the controls and grid are) is not yet mounted due to lazy loading.
If navigating from home to learn, the click is pointless as the controls are not visible.
The solution is to toggle the `disabled` state of the `controls-toggle-button` inside the viewport's route handler methods (`onHomeRoute` and `onLearnRoute`).