Function list_identities 

pub async fn list_identities(runner: &dyn CliRunner) -> Result<Vec<SshKey>>

List all identities currently loaded in the SSH agent.

Uses the native agent protocol when the agent feature is enabled, falling back to parsing ssh-add -l output otherwise.

Errors

Returns Error::AgentNotAvailable if the agent is not running, or Error::AgentOperationFailed if the agent protocol or CLI command fails.