Function extract_file_path 

pub fn extract_file_path(node_id: &str) -> Option<String>

Extract file path from a CodeNode ID.

IDs follow the pattern prefix:path/to/file.py::Name. This extracts path/to/file.py.

Examples:

• "func:brain/signal.py::fuse" → Some("brain/signal.py")
• "mod:brain/signal.py" → Some("brain/signal.py")
• "method:brain/store.py::Dual::get" → Some("brain/store.py")