Function parse_related_cases 

pub fn parse_related_cases(
    body: &str,
    section_start_line: usize,
    errors: &mut Vec<ParseError>,
) -> Vec<RelatedCase>

Parse the body of a ## Related Cases section into RelatedCase entries.

Each entry is a bullet - <case_path> followed by indented fields: description: <text> (required) and id: <NULID> (optional, written back).