Add LLM Cache statistics

### Self Checks

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### 1. Is this request related to a challenge you're experiencing? Tell me about your story.

I want to know if I have use llm cache. It is import to optimize the cost saving and performance through adjust the structure of the prompt and tool use

### 2. Additional context or comments

_No response_

### 3. Can you help us with this feature?

- [ ] I am interested in contributing to this feature.

El issue no menciona archivos, pruebas ni puntos de entrada. Primero localiza la implementación de la caché de LLM y aclara qué estadísticas se requieren y dónde deberían consultarlas los usuarios. Debería considerarse completado cuando las métricas de uso de la caché solicitadas estén disponibles y su comportamiento esperado esté documentado.

Escrito por el modelo de indexación a partir del texto del issue.