fix: remove unused imports, unnecessary mutable variables, and dead code

Co-authored-by: aider (openai/andrew/openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

src/modes/save.rs

@@ -245,7 +245,7 @@ pub fn mode_save(
     setup_item_metadata(conn, args, &item, tags)?; // Pass mutable reference
 
     // Use a transaction for database operations to ensure atomicity
-    let mut tx = conn.transaction()?;
+    let tx = conn.transaction()?;
 
     let item_meta = collect_item_meta(args);
     let item_id = item.id.ok_or_else(|| anyhow!("Item missing ID"))?;