Add canonical chunk plan source model

internal/framework/pipeline/chunk_validation.go

@@ -48,6 +48,14 @@ func validateAndCanonicalizeChunkResult(doc *source.SourceDocument, chunks []sou
 		if err := source.ValidateRef(doc, chunk.Ref); err != nil {
 			return nil, fmt.Errorf("chunk %q ref: %w", chunk.ID, err)
 		}
+		annotations, err := source.CanonicalizeChunkAnnotations(chunk.Annotations)
+		if err != nil {
+			return nil, fmt.Errorf("chunk %q annotations: %w", chunk.ID, err)
+		}
+		planAnnotations, err := source.CanonicalizeChunkAnnotations(chunk.PlanAnnotations)
+		if err != nil {
+			return nil, fmt.Errorf("chunk %q plan_annotations: %w", chunk.ID, err)
+		}
 
 		seenUnitIDs := make(map[int]struct{}, len(chunk.Units))
 		previousSourceIndex := -1
@@ -84,14 +92,16 @@ func validateAndCanonicalizeChunkResult(doc *source.SourceDocument, chunks []sou
 		}
 
 		canonicalChunks = append(canonicalChunks, source.Chunk{
-			ID:        chunk.ID,
-			SourceID:  chunk.SourceID,
-			Index:     chunk.Index,
-			Ref:       expectedRef,
-			Content:   append([]byte(nil), chunk.Content...),
-			MediaType: chunk.MediaType,
-			Units:     canonicalUnits,
-			Metadata:  cloneMetadata(chunk.Metadata),
+			ID:              chunk.ID,
+			SourceID:        chunk.SourceID,
+			Index:           chunk.Index,
+			Ref:             expectedRef,
+			Content:         append([]byte(nil), chunk.Content...),
+			MediaType:       chunk.MediaType,
+			Units:           canonicalUnits,
+			Metadata:        cloneMetadata(chunk.Metadata),
+			Annotations:     annotations,
+			PlanAnnotations: planAnnotations,
 		})
 	}