Small but critical improvements from documentation feedback not captured elsewhere

[nevencaplar]

1. Explain What does client=False do?
2. The “Division” warnings appear many times; suppress expected warnings.
3. “Ensemble Batch Showcase” -> “Creating and Applying User-Defined Functions”
4. In quickstart guide explain what lazy execution means
5. Ray notebook requires ray which is not installed during the tape install. Add ray installation on the top