Make item event responses compatible with strict schemas

internal/modules/dnd/extract/itemevents/extractor_test.go

@@ -81,6 +81,21 @@ func TestExtractPreservesInvalidCandidatesAndEmptyResults(t *testing.T) {
 	}
 }
 
+func TestExtractMapsNullableResponseFieldsToAbsentArtifactFields(t *testing.T) {
+	client := &fakeItemEventsLLMClient{content: []byte(`{"events":[{"name":"Hidden Cache","kind":"discovered","quantity":null,"from":null,"to":null,"source_refs":[{"start_segment":1,"end_segment":1}]}]}`)}
+	result, err := newExtractor(t, client).Extract(context.Background(), extractionRequest())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(result.Value.Events) != 1 {
+		t.Fatalf("events = %#v, want one", result.Value.Events)
+	}
+	event := result.Value.Events[0]
+	if event.Quantity != nil || event.From != "" || event.To != "" {
+		t.Fatalf("nullable response fields mapped to artifact values: %#v", event)
+	}
+}
+
 func TestExtractUsesSourceDocumentOrderForCandidates(t *testing.T) {
 	client := &fakeItemEventsLLMClient{response: extractionResponse{Events: []itemEventResponse{
 		{Name: "Later", Kind: "discovered", SourceRefs: responseRefs(10, 10)},