gptcli (v0.5.0)

Upgrade summaries from 3.5 turbo to 4.0o mini.

Thread summaries were previously completed using openai's gpt 3.5
turbo model. However, their recent release of 4.0o mini is 60% cheaper
and performs better.

https://openai.com/index/gpt-4o-mini-advancing-cost-efficient-intelligence/