Function extract_edges 

pub fn extract_edges(
    parse_results: &[ParseResult],
    resolver: &NameResolver,
) -> Vec<CodeEdge>

Extract all edges from parsed results.

Returns edges for:

• Containment (parent→child via parent_id)
• Imports (file→module)
• Inheritance (class→base class)
• Calls (detected via text scanning, best-effort)