[JULES-001] Infra: Inicializar ApiRegistry stub no VerticeAgent

[JuanCS-Dev]

Integrar a classe ApiRegistry da Vertex AI na classe base dos agentes para permitir a descoberta dinâmica de ferramentas, conforme o Blueprint 2026. TAG: JULES, ADK, INFRA

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.