Function extract_functions_from_ast 

pub fn extract_functions_from_ast(
    syntax: &SyntaxNode,
    remove_doc_comments: bool,
) -> Vec<FunctionInfo>

Extracts functions from a syntax node, returning a list of FunctionInfo.

We find all Fn items in the file. For each:

• Extract name (skip if none).
• Check attributes for #[test].
• Check visibility for pub.
• Extract signature line from the syntax.
• Extract body if present.