Restore tool cards on thread deserialization (#30053)

Release Notes:

- N/A

---------

Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>

crates/assistant_tools/src/delete_path_tool.rs

@@ -127,7 +127,7 @@ impl Tool for DeletePathTool {
 
             match delete {
                 Some(deletion_task) => match deletion_task.await {
-                    Ok(()) => Ok(format!("Deleted {path_str}")),
+                    Ok(()) => Ok(format!("Deleted {path_str}").into()),
                     Err(err) => Err(anyhow!("Failed to delete {path_str}: {err}")),
                 },
                 None => Err(anyhow!(