Feat/BugFix: Preserve sidebar scroll position on navigation

[codeEvolveZenith345]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines

• What kind of change does this PR introduce?

Bug fix

• What this PR does / why we need it:
  This PR fixes the sidebar navigation UX issue where clicking on any sidebar item causes the sidebar to scroll back to the top, making the selected item disappear from view. The fix:

• Adds sessionStorage to preserve and restore sidebar scroll position across page navigations
• Fixes critical JavaScript bug in change() function (assignment operator = changed to comparison ==)
• Fixes array overflow issue in loop condition (i <= ull.length +1 → i < ull.length)

• Which issue(s) this PR fixes:
  Fixes Bug: Sidebar scrolls to top on navigation, losing user's position #451

Before Recording.2026-01-23.162159.mp4

### After Recording.2026-01-23.162549.mp4

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[gemini-code-assist]

Summary of Changes

Hello @codeEvolveZenith345, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the user experience by addressing a long-standing sidebar navigation issue where the scroll position was lost upon page changes. It introduces a robust mechanism to persist the sidebar's scroll state and simultaneously resolves two critical JavaScript errors that could lead to unexpected behavior or crashes.

Highlights

• Sidebar Scroll Position Preservation: Implemented functionality to save and restore the sidebar's scroll position across page navigations using sessionStorage, preventing the sidebar from resetting to the top.
• Critical JavaScript Bug Fix: Corrected a critical JavaScript bug in the change() function where an assignment operator (=) was mistakenly used instead of a comparison operator (==), leading to incorrect logic.
• Array Overflow Prevention: Fixed an array overflow issue in a loop condition within the change() function, ensuring array elements are accessed within their valid bounds.

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[gemini-code-assist]

Code Review

This pull request does a great job of preserving the sidebar scroll position and fixing a couple of critical JavaScript bugs. My review includes suggestions to make the new scroll-saving logic more robust by handling cases where the sidebar element might not be present, removing an unused function parameter and a leftover debug statement, and cleaning up some code formatting for better readability.

[codeEvolveZenith345]

/cc @Arhell

[Arhell]

/lgtm