chore: add unit test and improve comment

src/shape.rs

@@ -826,7 +826,10 @@ impl ShapeSpan {
 
         let mut start_word = 0;
         for (end_lb, _) in unicode_linebreak::linebreaks(span) {
-            // Workaround for broken |> ligature in code fonts
+            // The unicode-linebreak crate treats the pipe character '|' as a break opportunity (BA/AL class).
+            // This causes ShapeSpan::build to split text like '|>' into separate ShapeWords.
+            // When these words are shaped independently, the font shaping engine cannot form ligatures that cross the word boundary.
+            // We manually check for the '|>' sequence during segmentation and skip the break opportunity to ensure they remain in the same shaping run.
             if end_lb > 0 && end_lb < span.len() {
                 let b = span.as_bytes();
                 if b[end_lb - 1] == b'|' && b[end_lb] == b'>' {