Day 33 update: smaller features and performance improvements

In the Day 33 update the product development team introduced several small but useful fixes: an inline indicator when switching models, the ability to enable/disable providers in the usage tracker, a rework of the Gemini provider, improved control of sub-agents, and polishing of the model selector. In addition, performance gains arrived for large Git repositories and long conversations containing many sub-agents; larger improvements are still in progress.