HS: breakpoint parse tests (+2 tests)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/playwright/generate-sx-tests.py

@@ -2551,6 +2551,15 @@ def generate_eval_only_test(test, idx):
         hs_expr = extract_hs_expr(m.group(2))
         assertions.append(f'    (assert-throws (fn () (eval-hs "{hs_expr}")))')
 
+    # Pattern 4: error("expr").toBeNull() — parsing/eval must not throw
+    if not assertions:
+        for m in re.finditer(
+            r'error\((["\x27])(.+?)\1\).*?toBeNull\(\)',
+            body, re.DOTALL
+        ):
+            hs_expr = extract_hs_expr(m.group(2))
+            assertions.append(f'    (hs-compile "{hs_expr}")')
+
     if not assertions:
         return None  # Can't convert this body pattern