Move chunks into the canonical source model

internal/modules/dnd/extract/spells/test_helpers_test.go

@@ -11,16 +11,19 @@ import (
 
 func promptExtractionRequest() contracts.ExtractionRequest {
 	doc := promptSourceDocument()
-	chunk := &contracts.SourceChunk{
-		ID:          "session-alpha:chunk:0",
-		SourceID:    doc.ID,
-		Index:       0,
-		StartUnitID: doc.Units[0].ID,
-		EndUnitID:   doc.Units[len(doc.Units)-1].ID,
-		Content:     []byte(`{"units":[1,2]}`),
-		MediaType:   "application/json",
-		Units:       append([]source.SourceUnit(nil), doc.Units...),
-		Metadata:    map[string]any{"ignored": "chunk metadata"},
+	chunk := &source.Chunk{
+		ID:       "session-alpha:chunk:0",
+		SourceID: doc.ID,
+		Index:    0,
+		Ref: source.SourceRef{
+			SourceID:    doc.ID,
+			StartUnitID: doc.Units[0].ID,
+			EndUnitID:   doc.Units[len(doc.Units)-1].ID,
+		},
+		Content:   []byte(`{"units":[1,2]}`),
+		MediaType: "application/json",
+		Units:     append([]source.SourceUnit(nil), doc.Units...),
+		Metadata:  map[string]any{"ignored": "chunk metadata"},
 	}
 	return contracts.ExtractionRequest{
 		Source: doc,