feat(google): add filtering options to vertexRagStore

[koistya]

Background

The Vertex RAG Store API supports filtering retrieval results via rag_file_ids and rag_retrieval_config. This enables dynamic, context-aware RAG queries where users can:

• Limit searches to specific files (e.g., files associated with a user session)
• Filter by metadata tags assigned when files were uploaded
• Set similarity/distance thresholds for quality control

Reference: Google Cloud AI Platform tool.proto

Summary

• Add ragFileIds parameter for file-level filtering
• Add metadataFilter parameter for tag-based filtering (recommended for large-scale filtering)
• Add vectorSimilarityThreshold and vectorDistanceThreshold for quality filtering
• Fix rag_resources structure to use array format per API spec

await streamText({
  model: vertex("gemini-2.0-flash"),
  tools: {
    rag: vertexRagStore({
      ragCorpus: "projects/my-project/locations/us-central1/ragCorpora/my-corpus",
      // Option 1: Filter by specific file IDs (for small sets)
      ragFileIds: ["file-1", "file-2"],
      // Option 2: Filter by metadata (recommended for large-scale filtering)
      metadataFilter: 'user_id = "user-123" AND project = "acme"',
      // Quality thresholds
      vectorSimilarityThreshold: 0.7,
      topK: 10,
    }),
  },
});

Checklist

• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added (for bug fixes / features - run pnpm changeset in the project root)
• I have reviewed this pull request (self-review)