fix: add missing clone_box impls for gzip and lz4 engines

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/compression_engine/gzip.rs

@@ -57,6 +57,10 @@ impl CompressionEngine for CompressionEngineGZip {
 
         Ok(Box::new(AutoFinishGzEncoder::new(gzip_write)))
     }
+
+    fn clone_box(&self) -> Box<dyn CompressionEngine> {
+        Box::new(self.clone())
+    }
 }
 
 #[cfg(feature = "gzip")]