Push flag pipeline_details_header_vue for detail views

What does this MR do and why?

Resolves this problem #414756 (comment 1429939271) found in the feedback issue. Previously the flag was only pushed for show which resulted in the header not getting mounted for detail views (due to flag state).

Screenshots or screen recordings

How to set up and validate locally

Visit a URL like http://gdk.test:3000/${namespace}/${project}/-/pipelines/${ID}/builds and ensure the pipeline header is mounted.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #394768 (closed)