Commit rapid diff file header dropdown overlaps comment box

Summary

In the commit file diff header on the commits page, the dropdown menu sometimes appears in the wrong place and is blocked by the comment box, making it difficult or impossible to use.

Steps to reproduce

⚠️ These steps are based on the currently known information and may not be fully reliable.

• Log in to GitLab.com with an account that can access this commit

• Ensure config/feature_flags/beta/blob_edit_refactor.yml is collapsed (so you only see the file diff header row).

• Interact with the file diff header dropdown (e.g., open the dropdown on the header).

Relevant screenshots / recordings

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Environment

• Browser: Firefox 147.0.3 with all extensions disabled