fix(legacy-html): prevent scroll jump when opening header pickers

[Sahilshrma31]

Description

Fixes an unintended page scroll jump when opening sticky header picker dropdowns in legacy HTML docs.

Validation

I reproduced and verified on a generated legacy HTML page (out/fs.html) and in browser behavior matching the reported scenario.

Reproduction steps

Open an API docs page.
Scroll to the middle of the page.
Open sticky header pickers (Table of contents, Index, Other versions, Options).

Before

Screen.Recording.2026-04-15.at.11.01.24.PM.mov

Opening a picker causes the page to jump upward unexpectedly.

After

Screen.Recording.2026-04-15.at.11.02.03.PM.mov

Opening a picker no longer changes scroll position; only the dropdown opens.

Related Issues

Fixes #764

Check List

• I have read the Contributing Guidelines and made commit messages that follow the guideline.
• I have run node --run test and all tests passed.
• I have check code formatting with node --run format & node --run lint.
• I've covered new added functionality with unit tests if necessary.

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Project	Deployment	Actions	Updated (UTC)
api-docs-tooling	Ready	Preview	Apr 15, 2026 5:37pm

[cursor]

PR Summary

Low Risk
Low risk: small client-side UI tweak limited to legacy HTML picker focus behavior, with a guarded fallback for browsers that don’t support preventScroll.

Overview
Prevents an unintended scroll jump when opening legacy HTML header picker dropdowns by focusing the first dropdown link with focus({ preventScroll: true }).

Adds a null check and a try/catch fallback to plain focus() for browsers that don’t support the preventScroll option.

^{Reviewed by Cursor Bugbot for commit d6a4bff. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.44%. Comparing base (3d00fa8) to head (d6a4bff).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #773   +/-   ##
=======================================
  Coverage   78.43%   78.44%           
=======================================
  Files         157      157           
  Lines       13962    13967    +5     
  Branches     1152     1152           
=======================================
+ Hits        10951    10956    +5     
  Misses       3006     3006           
  Partials        5        5           

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