fix: guard against empty path in NewFileReader after filepath.Clean

filepath.Clean("") returns "." which opens current directory instead
of failing. Add explicit empty-path check before file operations.

Author: mchmarny

pkg/serializer/reader.go

@@ -147,6 +147,10 @@ func NewFileReader(format Format, filePath string) (*Reader, error) {
 		return nil, errors.New(errors.ErrCodeInvalidRequest, "table format does not support deserialization")
 	}
 
+	if filePath == "" {
+		return nil, errors.New(errors.ErrCodeInvalidRequest, "failed to open file: path is empty")
+	}
+
 	// If the filePath is a URL or special scheme, handle accordingly
 	var file *os.File
 	var err error