fix: resolve compilation errors by fixing mutable references and removing unused imports

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

src/modes/update.rs

@@ -101,7 +101,7 @@ pub fn mode_update(
 
             // 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)?;
+            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 {:?}",