Function extract_paragraph_trace 

pub fn extract_paragraph_trace(stdout: &str) -> String

Extracts the \tracingparagraphs trace from TeX’s terminal output: everything from @firstpass (or @secondpass, if the first pass is skipped) up to the end of the trace.

After the trace, TeX may print underfull/overfull box warnings when it packages the broken lines (TeX.2021.660 and TeX.2021.663). These are not part of the line breaking trace, so extraction stops there too.