Add LoginScript to OneKey

Can the OneKey function be enhanced to include a login script, such as executing "su" to switch to the root user after successful login? I see that this feature is already available in the Expect type of OneKey function, but I would like to combine the two. After logging in normally with OneKey and the key file, I would like to use the Expect function to switch to the root user or execute other commands.

The issue names no files or tests. Start by locating the existing OneKey and Expect implementations, then determine how a login script should run after key-based login. Done means OneKey supports post-login commands such as switching to root with su while preserving its normal login behavior, with coverage for this path if the project provides it.

Written by the indexing model from the issue text.