Function remove_unwanted_lines_keep_docs 

pub fn remove_unwanted_lines_keep_docs(s: String) -> String

Removes attribute lines (#[...]) and normal // comment lines, but keeps doc lines (///, //!) when remove_doc_comments = false. Also handles inline // in code lines by truncation, preserving whitespace.

Doc lines are kept intact. Inline // in code lines still gets truncated.