Function write_ssh_config_entry 

pub fn write_ssh_config_entry(
    alias: &str,
    hostname: &str,
    user: Option<&str>,
    port: Option<u16>,
    identity_file: Option<&str>,
    jump_host: Option<&str>,
) -> Result<PathBuf, HostError>

Write a new host entry to the user’s SSH config file

Appends a Host block to ~/.ssh/config with the provided settings. Creates the file and directory if they don’t exist.