Function validate_agent_chains 

pub fn validate_agent_chains(
    registry: &AgentRegistry,
    sources: &AgentResolutionSources,
    colors: Colors,
)

Validates that agent chains are properly configured.

Displays an error and exits if the agent chains are not configured.

Arguments

• registry - The agent registry
• sources - Description of config sources consulted for resolution
• colors - Color configuration for output