Suggestion: add message queue for the transport

Benefits:
- Asynchronous communication – decouples sender and receiver
- Built-in rate control – buffer messages and control processing speed
- Better fault tolerance – messages are not lost if consumer is down
- Scalable – easy to add more consumers to handle load
- Improves system resilience – smooths traffic spikes (e.g., burst handling)
- Flexible architecture – enables event-driven or microservices patterns

The issue proposes adding a message queue to the A2A transport layer but does not specify where in the codebase to start. First, examine the existing transport implementation in the repository to understand the current communication flow. Then, research how message queues (like RabbitMQ, Kafka, or in-memory options) could be integrated. Determine the scope: whether this is a core protocol change or a server-side enhancement, and define what 'done' looks like in terms of design and implementation.

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