Strengthen validation retries and checkpoint safety

internal/modules/dnd/validate/combatturns/shape/validator_test.go

@@ -41,6 +41,9 @@ func TestValidateRejectsEveryOwnedShapeBoundary(t *testing.T) {
 			if err != nil || result.Approved || result.ReasonCode != ReasonCode {
 				t.Fatalf("Validator result = %#v, %v; want shape rejection", result, err)
 			}
+			if err := contracts.ValidateValidationResult(result); err != nil {
+				t.Fatalf("ValidateValidationResult() error = %v for %#v", err, result)
+			}
 		})
 	}
 }