Instead of erroring on context length exceeded after 3 attempts, ask the user what to do

[salman1993]

Currently, we try to attempt truncation 3 times with 90%, 80%, 70% msgs - then fail.

Error: Context length exceeds limits even after multiple attempts to truncate. 

Instead, we can ask the user whether we should attempt futher truncation OR to exit so that user can start a fresh session if they want