[Feat]: Allow alternative URL for agent card

### Is your feature request related to a problem? Please describe.

I'd like to be able to test agents that don't use the .well-known endpoint for advertising the agent card without having to use --skip-agent-card

### Describe the solution you'd like

A command line parameter to provide an alternative agent card url

### Describe alternatives you've considered

We could use the /v1/card HTTP endpoint if .well-known is not available. This doesn't solve the problem for people putting agent cards in registries though.

It might also be nice to reference a local file as the agent card.

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct