refactor: use compression_engine.open for file handling in update mode

src/modes/update.rs

@@ -83,10 +83,10 @@ pub fn mode_update(
             let mut digest_engine = digest_engine::get_digest_engine(digest_type);
             
             // Read file content and update digest
-            let mut file = std::fs::File::open(&item_path)?;
+            let mut reader = compression_engine.open(item_path)?;
             let mut buffer = [0; 4096];
             loop {
-                let bytes_read = file.read(&mut buffer)?;
+                let bytes_read = reader.read(&mut buffer)?;
                 if bytes_read == 0 {
                     break;
                 }