fix: correct mutable reference handling and remove unused variables

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/modes/update.rs

@@ -100,8 +100,8 @@ pub fn mode_update(
             debug!("DIGEST: {}", digest_value);
 
             // Save digest to meta using the common function
-            // Pass the transaction directly instead of calling into_inner()
-            store_item_digest_value(&tx, item.clone(), digest_type, digest_value)?;
+            // Pass the transaction as mutable reference
+            store_item_digest_value(&mut tx, item.clone(), digest_type, digest_value)?;
         } else {
             debug!(
                 "MAIN: Unable to update digest of item due to missing file {:?}",