fix(bytetrack): send correct events when opening lines

a bit of test cleanup

ärrår

feeel

SPLIT

fix: sned correct updates on <CR>

src/nvim/change.c

@@ -1677,6 +1677,9 @@ int open_line(
         truncate_spaces(saved_line);
       }
       ml_replace(curwin->w_cursor.lnum, saved_line, false);
+      extmark_splice_cols(
+          curbuf, (int)curwin->w_cursor.lnum,
+          0, curwin->w_cursor.col, (int)STRLEN(saved_line), kExtmarkUndo);
       saved_line = NULL;
       if (did_append) {
         changed_lines(curwin->w_cursor.lnum, curwin->w_cursor.col,