Add example: connect a CrewAI agent to AIR Blackbox

[shotwellj]

What

Create a simple example in an examples/ directory showing how to connect a CrewAI agent to AIR Blackbox end-to-end.

Why

The quickstart shows how to point a basic OpenAI client at the Gateway, but we don't have a working example for multi-agent frameworks. A CrewAI example would help people see how the trust plugin and Gateway work together.

Where to start

• Create examples/crewai-example/ with a simple agent
• Show the one-line base_url change
• Include a README with setup steps
• Bonus: show the traces in Jaeger after running it

This doesn't require deep knowledge of the codebase — just familiarity with CrewAI and following the quickstart.