Glossary tooltip overlaps the sticky header on the Contributor Handbook

[ravichudasama01]

When hovering over glossary terms on the Contributor Handbook, the glossary tooltip is displayed above the sticky header, causing it to overlap the navigation bar. This appears to be a stacking order (z-index) issue where the tooltip has a higher priority than the header.

The sticky header should remain above page content and interactive elements, or the tooltip should be positioned so that it does not overlap the header.

Steps to Reproduce
Visit the Contributor Handbook page.
Scroll until the sticky header is visible.
Hover over a glossary term near the top of the page (e.g., Open Source).
Observe the tooltip position.

Expected Result
The glossary tooltip should appear below the sticky header or behind it, without overlapping the navigation.

Actual Result
The glossary tooltip is rendered above the sticky header, overlapping the navigation and indicating an incorrect stacking order.