test: add Gate 3 numerical oracle contracts

scripts/check_mutation_score.py

@@ -10,6 +10,9 @@ from pathlib import Path
 from typing import Any
 
 
+DEFAULT_MUTATION_SCORE_MINIMUM = 85.0
+
+
 def mutation_score(stats: dict[str, Any]) -> tuple[int, int, float]:
     """Return killed, total, and percentage after validating mutmut statistics."""
     killed = stats.get("killed")
@@ -48,7 +51,7 @@ def validate_mutation_stats(
 def _parser() -> argparse.ArgumentParser:
     parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument("stats", type=Path, help="mutmut-cicd-stats.json path")
-    parser.add_argument("--minimum", type=float, required=True)
+    parser.add_argument("--minimum", type=float, default=DEFAULT_MUTATION_SCORE_MINIMUM)
     return parser