cli: prevent panic when elicitation is requested in non-interactive s…

[Pnkcaht]

What I did

• Prevented a panic when elicitation (e.g. user_prompt / OAuth authorization) is triggered during non-interactive cagent exec sessions
• Added defensive checks for elicitation metadata to avoid unsafe type assertions
• Gracefully skipped elicitation when user interaction is not possible, resuming the runtime with a declined response
• Ensured non-interactive executions fail safely instead of crashing

Related issue

• Fixes user_prompt panic in noninteractive mode #1554 (panic when user_prompt is invoked in non-interactive session)

Before

• cagent exec could invoke elicitation tools in non-interactive sessions
• The CLI assumed cagent/server_url was always present and a valid string
• Missing or nil metadata caused a panic:
  • interface conversion: interface {} is nil, not string
• The process crashed instead of exiting cleanly

After

• Elicitation metadata is validated before use
• Non-interactive sessions no longer trigger unsafe type assertions
• Elicitation is safely skipped when user input is not possible
• cagent exec exits cleanly without panicking

Test

Screenshot Yaml (test)

Commands

• go test ./...
• cagent exec ./agent.yml "it's not working"
• echo "it's not working" | cagent exec ./agent.yml -

Result

• Verified no panic occurs when using a YAML config with a non-existent model (model: fake)
• Verified the command exits gracefully and prints a controlled error message

Screenshot Result (test)