test(benchmarks): add A/B task fixtures with hidden checks

Ten small Python tasks, each failing on the fixture and passing with a
reference solution, including workflow expectations for a small change, a
bugfix, and a delegable change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/benchmarks/tasks/06-refactor-duplication/repo/app/report.py

@@ -0,0 +1,20 @@
+def sales_report(rows):
+    lines = []
+    for name, amount in rows:
+        label = name.strip().title()
+        value = f"{amount:,.2f}"
+        lines.append(f"{label:<20}{value:>12}")
+    total = sum(amount for _, amount in rows)
+    lines.append(f"{'Total':<20}{total:>12,.2f}")
+    return "\n".join(lines)
+
+
+def cost_report(rows):
+    lines = []
+    for name, amount in rows:
+        label = name.strip().title()
+        value = f"{amount:,.2f}"
+        lines.append(f"{label:<20}{value:>12}")
+    total = sum(amount for _, amount in rows)
+    lines.append(f"{'Total':<20}{total:>12,.2f}")
+    return "\n".join(lines)