feat(legacy-html): mirror sidebar scroll changes

[flakey5]

Mirror to nodejs/node#60410

Description

Validation

Related Issues

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.

[vercel]

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Project	Deployment	Preview	Updated (UTC)
api-docs-tooling	Ready	Preview	Nov 24, 2025 9:54pm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.10%. Comparing base (d980054) to head (f9a5c35).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #492   +/-   ##
=======================================
  Coverage   74.10%   74.10%           
=======================================
  Files         111      111           
  Lines       10562    10562           
  Branches      701      701           
=======================================
  Hits         7827     7827           
  Misses       2732     2732           
  Partials        3        3           

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[AugustinMauroy]

LGMT !