Function handle_agent 

pub fn handle_agent(
    cmd: AgentCommand,
    repo_path: PathBuf,
    env_config: &EnvironmentConfig,
    passphrase_provider: Arc<dyn PassphraseProvider + Send + Sync>,
) -> Result<()>

Dispatch an auths id agent … subcommand.

Args:

• cmd: The parsed agent command.
• repo_path: Resolved registry repository path.
• env_config: Environment configuration for context building.
• passphrase_provider: Passphrase source for key access.

Usage:

handle_agent(cmd, repo_path, &env_config, passphrase_provider)?;