Function parse_environment_variables 

pub fn parse_environment_variables(
    stdout: &str,
    stderr: &str,
    options: &[OptionSpec],
) -> Vec<EnvVarSpec>

Parse environment variables from help text.

Looks for patterns like:

• “Can be set via $VAR”
• “Uses VAR environment variable”
• “VAR (default: value)”
• “Set VAR to …”
• Option descriptions mentioning environment variables