Function execute_streaming 

pub async fn execute_streaming(
    command: &str,
    cwd: Option<&str>,
    env: Option<&HashMap<String, String>>,
    timeout_secs: Option<u64>,
    tx: Sender<StreamChunk>,
) -> Result<StreamingCommandResult>

Spawn a shell command and stream its output.

Returns the final CommandResult-like summary after the process exits. tx receives ShellOutput and ShellLifecycle chunks in real time.