Draft: Scaffold AI Review tab on MR page behind feature flag

Marc Shawrequested to merge
ms/mr-ai-tab-scaffold into master

What does this MR do?

Scaffolds an empty "AI Review" tab on the merge request page behind the mr_ai_review_tab wip feature flag.

The tab intentionally has no real content yet — only the plumbing (route, controller action, navigation entry, Vue mount) is wired up. Follow-up MRs will iterate on what the tab actually surfaces.

How to test

Feature.enable(:mr_ai_review_tab, Group.find_by_full_path('gitlab-org'))

Visit any merge request — the "AI Review" tab should appear after Reports, before Changes.

Related

Merge request reports