chore(validation): seed reproducible Crosscheck defect

validation/crosscheck_v2/bounded_slice.py

@@ -0,0 +1,9 @@
+"""Small validation fixture for the Crosscheck durable-finding checkpoint."""
+
+
+def bounded_slice(values: list[int], limit: int) -> list[int]:
+    """Return at most ``limit`` values, with nonpositive limits returning none."""
+
+    if limit <= 0:
+        return values
+    return values[:limit]

validation/crosscheck_v2/test_bounded_slice.py

@@ -0,0 +1,11 @@
+"""Executable regression for the deliberate validation defect."""
+
+from bounded_slice import bounded_slice
+
+
+def test_nonpositive_limit_returns_no_values() -> None:
+    assert bounded_slice([1, 2, 3], 0) == []
+
+
+if __name__ == "__main__":
+    test_nonpositive_limit_returns_no_values()