Complete Phase 2 Go normalization foundation

internal/core/schema/transcript.go

@@ -47,14 +47,13 @@ func ParseSourceTranscriptJSON(raw []byte) (*SourceTranscript, error) {
 		return nil, err
 	}
 
-	if len(segmentsRaw) == 0 {
-		return nil, &ParseError{Message: "transcript must contain at least one segment"}
-	}
-
 	var segments []SourceSegment
 	if err := json.Unmarshal(segmentsRaw, &segments); err != nil {
 		return nil, &ParseError{Message: fmt.Sprintf("failed to parse segments: %v", err)}
 	}
+	if len(segments) == 0 {
+		return nil, &ParseError{Message: "transcript must contain at least one segment"}
+	}
 
 	if err := validateSourceSegments(segments); err != nil {
 		return nil, err