Feature: Added in-page navigation and back-to-top links to LFX 2026 page

[kanishksingh23]

Description

• Added id="top" anchor at the top of the page
• Added an "On this page" navigation block linking to Spring, Summer, Fall, and Additional Information sections
• Added stable anchor IDs ({#spring-2026}, {#summer-2026}, {#fall-2026}, {#additional-info}) to each term heading
• Added "↑ Back to top" links at the end of each term section
• Added missing Summer 2026 and Fall 2026 project sections
• Added supporting CSS styles in Programs.style.js for the nav and back-to-top link

This PR fixes #7704

Notes for Reviewers

• Only two files changed: lfx-2026.mdx and Programs.style.js
• Fall 2026 section includes a placeholder note since projects are announced on July 2nd, 2026
• Styles use existing theme variables for dark/light mode compatibility

Before SS

After SS

Signed commits

• Yes, I signed my commits.

[github-actions]

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[kanishksingh23]

@saurabhraghuvanshii, please take a look.

[saurabhraghuvanshii]

@kanishksingh23 I think ui is not good it should be like dropdown menu and on right side of screen and there should be only one icon on bottom of screen of right to go on top and that botton should only visible when we reach at bottom of page.

[kanishksingh23]

@saurabhraghuvanshii,done

[banana-three-join]

@kanishksingh23 Do you have a preview of the new look?

[kanishksingh23]

@saurabhraghuvanshii, @banana-three-join, link for the new preview - https://layer5.io/pr-preview/pr-7707/programs/lfx/2026
The new look

[banana-three-join]

@kanishksingh23 Good job! It looks way better and I was testing in the PR and it's behavior is as expected. The only thing that I would say is that, maybe it's background and text should support changes between light and dark mode. Aside from that, maybe you could add some more padding on the left of the Table of Content so the markers don't look as close to the edge. Other than that, it looks great!