Migrate ordinary I/O from confined file helpers

internal/contracts/bounds.go

@@ -164,7 +164,7 @@ func loadTranscriptSegmentIDs(path string) (map[int]struct{}, error) {
 }
 
 func readContractResult(path string, limit int64, category string) ([]byte, error) {
-	data, err := fileops.ReadRegularFile(path, limit)
+	data, err := fileops.ReadFileBounded(path, limit)
 	if err != nil {
 		return nil, fmt.Errorf("%s exceeds or cannot be read within %d-byte limit: %w", category, limit, err)
 	}