🐛 Bug: Section header does not highlight when navigating from Table of Contents

Describe the bug

When clicking an item in the Table of Contents, the page scrolls to the corresponding section correctly. However, the header of that section does not change color or highlight to indicate that it is the active section. This makes it difficult for users to visually identify the currently focused section.

Steps To Reproduce

1. Go to the https://json-schema.org/learn/getting-started-step-by-step#introduction-to-json-schema
   2.Scroll down to the Table of Contents.
2. Click on any item from the list.
3. The page scrolls to the corresponding section.
4. Observe that the header of that section does not change color to indicate it is active.

Expected Behavior

When a user clicks on an item in the Table of Contents, the page should scroll to the corresponding section and the header of that section should change color to indicate it is the active section.

Screenshots

https://github.com/user-attachments/assets/f950ccfc-0682-4696-aa72-7ab41f34ff22

Device Information [optional]

- OS:
- Browser:
- version:

Are you working on this issue?

No

Do you think this work might require an [Architectural Decision Record (ADR)]? (significant or noteworthy)

Yes

Reproduce the issue on the linked getting-started-step-by-step page by selecting entries in the Table of Contents. Inspect the Table of Contents and section-header behavior around the linked introduction-to-json-schema anchor, then verify that the selected section header receives the expected visual highlight after navigation.