Branch should be preserved when moving from the pipeline editor to the repository

What does this MR do and why?

This MR updates the current behaviour on the pipeline editor page. The branch selector now reloads the page. This is needed to update the links in the sidebar, which are rendered on the Rails side. With this change, when the user selects a branch on the pipeline editor page, this selection is respected for the repository link.

References

• #480681 (closed)

Screenshots or screen recordings

Before	After
Screen_Recording_2025-06-30_at_17.04.32	Screen_Recording_2025-06-30_at_17.03.30

How to set up and validate locally

1. Create multiple branches and a simple .gitlab-ci.yml config.
2. Navigate to Build -> Pipeline editor and select another branch in the branch selector
3. Verify the link to the repository updated after selection.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #480681 (closed)