StickyNavigationIndicator class

A sticky navigation indicator.

This indicator animates between navigation items with a "sticky" effect, stretching and contracting smoothly as the selection changes.

Behavior

At rest (not transitioning): The indicator is displayed in the center of the selected item with equal padding on both ends.

During transition:

• The old item's indicator shrinks towards the new item (padding increases on the side facing the new item)
• The new item's indicator grows from the direction of the old item (padding decreases on the side facing the old item)

This creates a "sticky" stretching effect as if the indicator is being pulled from one item to another.