Fix documentation fragment anchor offsets

[p1930n]

This PR is a fresh replacement for #55703. The previous PR went through a somewhat messy revision process, so I opened this one from a clean branch.

The change is based on the issues and related previous PRs:

• Fixes Scrolling to target element hides headings #29909
• Fixes Anchor offset overlaps controls #51923
• Related: Anchor offset overlaps controls #32695, Fix anchor offset overlap blocking UI interactions #51954, Fix documentation fragment anchor offsets #55703

Validation

• git diff --check

Not run locally: full Hugo build. This worktree does not have hugo or node_modules installed.

AI disclosure

I planned this change myself. The code was written with AI assistance, then reviewed again by me before submission.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign katcosgrove for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[p1930n]

I doube checked this new PR, I think this is ready for review now.