feature: `chat` failure message need more context

[esnible]

Feature Description

I did rossoctl agents chat weather-service --message "is it hot in cairo", which failed with

Error: failed to send HTTP request: Post "http://weather-service.team1.svc.cluster.local:8080/": dial tcp: lookup weather-service.team1.svc.cluster.local: no such host

This issue is to improve the error message.

• Does chat use the Rossoctl HTTP API to chat, or get the A2A endpoint from Rossoctl's HTTP API?
  • It should do the former if it is to talk to agents with no exposed HttpRoute
• What API is claiming the endpoint is weather-service.team1.svc.cluster.local ? Should rossoctl-backend implementation return the HttpRoute endpoint, or the Service endpoint, or both?

Proposed Solution

Check for common misconfigurations when an Agent does not have an address reachable by the CLI, and report them and their fixes instead of merely failing.

Want to contribute?

• I would like to work on this issue.

Additional Context

No response