fix: Tourist Scheduling System Real Agents Demo

[muscariello]

Title: Fix Tourist Scheduling System "Real Agents" Demo

Description

This update resolves several critical issues preventing the "Real Agents" demo (./run.sh --real-agents) from running successfully. The fixes span the transport layer, data serialization, and process orchestration.

Key Issues Addressed

1. Transport Layer Crash (request_metadata)

   • Problem: The SLIM transport layer was passing a request_metadata argument to the underlying Google ADK transport, which caused a TypeError as the ADK does not support this argument.
   • Fix: Implemented CustomSRPCTransport in src/core/slim_transport.py to intercept calls and filter out request_metadata while preserving extensions before delegating to the ADK.

2. Serialization Error (ValueError: Unexpected type)

   • Problem: The agents were attempting to send raw Pydantic models (e.g., Assignment, Proposal) directly to the ADK. The ADK's Protobuf serializer requires standard Python types (dicts/lists), resulting in a crash.
   • Fix: Updated src/agents/tools.py to explicitly serialize Pydantic models using .model_dump(mode='json') before transmission.

[lgecse]

LGTM!