Fix c19 delimiter fallback in tail_threshold_v2 reader

evaluation/tail/tail_threshold_code_v2/src/eval/tail_threshold_v2/runner.py

@@ -139,6 +139,12 @@ def _sniff_delimiter(path: Path) -> str:
 
 def _read_csv_rows(path: Path) -> tuple[list[str], list[dict[str, str]]]:
     delimiter = _sniff_delimiter(path)
+    with path.open("r", encoding="utf-8-sig", newline="") as handle:
+        first_line = handle.readline()
+    # Some quoted comma CSVs with long text fields can be mis-sniffed as pipe.
+    # If there are commas in the header line but no pipes, prefer comma parsing.
+    if delimiter == "|" and "," in first_line and "|" not in first_line:
+        delimiter = ","
     with path.open("r", encoding="utf-8-sig", newline="") as handle:
         reader = csv.DictReader(handle, delimiter=delimiter)
         rows = [dict(row) for row in reader]