The volume usage checker script in must-gather outputs critical error messages 
    to stdout instead of stderr. When disk space exceeds the configured limit, the 
    error message "Disk usage exceeds the volume percentage..." is written to stdout 
    (line 98 in pkg/cli/admin/mustgather/mustgather.go), which is inconsistent with 
    Unix conventions and the error handling pattern used elsewhere in the must-gather 
    codebase.

    Always - the volumeUsageCheckerScript uses plain 'echo' commands which always 
    write to stdout.

   1. Run `oc adm must-gather` with output redirection: `oc adm must-gather > output.log`
    2. Trigger disk usage to exceed the --volume-percentage limit (default 70%)
    3. Observe that the critical error "Disk usage exceeds the volume percentage..." 
       is written to output.log instead of appearing on the terminal

        The disk usage error message goes to stdout and gets captured by output 
    redirection, potentially making the error invisible to the user if they're 
    redirecting stdout to a file.

        The disk usage error message should be written to stderr (using '>&2' 
    redirection) so it:
    - Remains visible on the terminal even when stdout is redirected
    - Follows Unix conventions where errors go to stderr
    - Matches the pattern used elsewhere in must-gather (e.g., lines 1252-1267 
      use fmt.Fprintf(o.ErrOut, ...) for errors)