fix(multiplayer): complete live results atomically

server/domain/result.go

@@ -102,6 +102,9 @@ func (s *ResultStore) Submit(resultID string, result MatchResult, binding Worklo
 	if resultID == "" || !sameBinding(s.expected, binding) {
 		return ResultReceipt{}, false, ErrResultBinding
 	}
+	if now.IsZero() {
+		return ResultReceipt{}, false, ErrResultInvalid
+	}
 	if err := validateResult(s.expected, result); err != nil {
 		return ResultReceipt{}, false, err
 	}

server/domain/result_test.go

@@ -36,6 +36,17 @@ func TestResultStoreBindsWorkloadAndMakesIdenticalDuplicateInert(t *testing.T) {
 	}
 }
 
+func TestResultStoreRejectsMissingAuthoritativeTime(t *testing.T) {
+	binding := testBinding()
+	store, err := NewResultStore(binding)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, _, err := store.Submit("result-1", testResult(), binding, time.Time{}); !errors.Is(err, ErrResultInvalid) {
+		t.Fatalf("zero-time result error = %v", err)
+	}
+}
+
 func TestConflictingResultIsInertAndIntegritySuppressesRating(t *testing.T) {
 	now := time.Unix(1000, 0)
 	binding := testBinding()