Function run_pty 

pub fn run_pty(
    program: &Path,
    args: &[&str],
    cwd: &Path,
    home: &Path,
    input: &str,
) -> CmdOutput

Runs a command in a PTY and captures output.

Notes:

• PTY output is a merged stream (stdout+stderr); we populate stdout.
• This helper is intentionally minimal; interactive parity tests can extend it to incremental reads/writes.