Function for_each_text_content 

pub fn for_each_text_content<F>(document: &Document, f: &mut F)
where
    F: FnMut(&TextContent),

Visits every text content node in the document, invoking the callback for each.

Traverses the full document tree including session titles, paragraph lines, list item text, definition subjects, and annotation bodies. Useful for extracting inline references or performing text-level analysis.