Default Context Window

I always prefer to use the long context window models, but it always defaults to the regular context window. I have no way to make it always use the long context window, even when I go to start a new session. Yes, it will keep the previous model with the long context window, but if I want to switch to a different model, I now need to manually select the long context window for that. Even if I had previously used the long context window for that model, there should be some sort of a setting where it can just always default to long or short context window.

No files, tests, or entry points are named. Start by locating the model-selection flow and existing application settings, then determine where a persistent short- or long-context preference belongs. Done means a user can choose a default context-window preference and new sessions honor it when switching models.

Written by the indexing model from the issue text.