Function sudoers_user_scoped_line 

pub fn sudoers_user_scoped_line(
    username: &str,
    choice: SudoTimestampChoice,
) -> String

What: Build a user-scoped Defaults line alternative for the instructions pane.

Inputs:

• username: Target login name (typically $USER).
• choice: Selected cache duration.

Output:

• Two lines: marker comment plus Defaults:username timestamp_timeout=….

Details:

• Safer than a global Defaults on shared systems; requires correct username spelling.