Fix GraphQL validation error in Duo Agentic Chat

What does this MR do and why?

Fixes a GraphQL validation error that occurred when the Duo Agentic Chat component queried for configured agents. The resolver for aiCatalogConfiguredItems enforces an exactly_one_of validation requiring either projectId or groupId, but not both.

This MR updates the query variables to conditionally pass only one of these parameters, preferring projectId when available.

before	after

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Related issues

https://gitlab.com/gitlab-org/modelops/applied-ml/code-suggestions/ai-assist/-/issues/1404+

Steps to reproduce

1. Visit search page: http://127.0.0.1:3333/search?group_id=1000000&scope=blobs&search=test
2. Open chat. If this doesn't work you'll see error in the chat:

Error: One and only one of \[groupId, projectId\] arguments is required.
Error: GraphQL error: One and only one of \[groupId, projectId\] arguments is required.

I can't see it currently in my gdk but I do see it in the prod.