s&box: Reading player input with Input.Down/Pressed/Released and AnalogMove/AnalogLook

In s&box, reading player input requires using the Input class with named action strings, not Unity-style KeyCode enums. Developers don't know the difference between Input.Down (held), Input.Pressed (just pressed this frame), and Input.Released (just released). Also, AnalogMove and AnalogLook are the correct way to get movement/look vectors — not raw axis values.