Add AI Catalog button to the Duo navigation rail

What does this MR do and why?

Adds an AI catalog button to the bottom of the Duo navigation rail to improve discoverability of the AI catalog

• The button opens the catalog in a new tab
• It's only visible when the rest of the Duo navigation rail is visible to the user
• The tooltip reads "Duo AI Catalog"

Event tracking to come in a second MR

References

• Related to Add AI Catalog icon to the Duo right‑side rail ... (#592493 - closed) • Allison Villa • 18.11

Screenshots or screen recordings

Screen recording of me clicking on the new button and showing what it looks like on a narrow viewport.

On hover

How to set up and validate locally

1. Prerequisite: Have GitLab Duo set up in your GDK
   • Have a Duo-enabled group and project in your GDK created by the Duo setup task above
   • If you don’t see “AI Catalog” under Explore in your GDK, check that the global_ai_catalog feature flag is enabled
2. Use the new AI catalog button at the bottom of the navigation rail
3. Resize your window to test the button behaviour at different viewport widths

MR acceptance checklist

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