fix(campaign): a record always says how many actions named no producer

An omitted count reads the same as a run recorded before actions carried a
source, so the two cannot be told apart by anything downstream.

cmd/internal-tools/campaign/campaign_test.go

@@ -138,14 +138,19 @@ func TestRunCampaign_RecordsDispatchedActionsNotSteps(t *testing.T) {
 }
 
 // A run that never produced a readable trace still has to carry the field, so
-// analysis can tell a zero-action run from a file written before the count.
-func TestRunRecord_AlwaysCarriesTheActionCount(t *testing.T) {
+// analysis can tell a zero-action run from a file written before the count. The
+// same holds for the unattributed count: a run whose every action named its
+// producer says so with a zero, and a file that says nothing is one recorded
+// before actions named one at all.
+func TestRunRecord_AlwaysCarriesTheActionCounts(t *testing.T) {
 	body, err := json.Marshal(runRecord{Seed: 7, TraceError: "no run directory with meta.json"})
 	if err != nil {
 		t.Fatal(err)
 	}
-	if !strings.Contains(string(body), `"actions":0`) {
-		t.Errorf("record %s omits the action count", body)
+	for _, field := range []string{`"actions":0`, `"unattributed_actions":0`} {
+		if !strings.Contains(string(body), field) {
+			t.Errorf("record %s omits %s", body, field)
+		}
 	}
 }