Update UX of "Fix pipeline button"

What does this MR do and why?

This MR moves the position of the Duo Workflow component down and changes the text for a more coherent look across different scenarios.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. In GDK open a merge request with a failed pipeline, open the pipeline tabs
2. Notice there is no button with "Fix with Duo"
3. In Rails console enable the feature flag

Feature.enable(:ai_duo_agent_fix_pipeline_button)

4. Go back to the merge request and refresh
5. Notice the button "Fix with Duo"
6. Optionally, if you've setup AI gateway and a runner, click on the button and verify it starts a Flow.

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Related to #569100 (closed)