zkit: provider agnostic Agent toolkit

A hard prompt is a sequence of tokens. In prompt engineering, we contrast them with soft prompts, which are internal model states. Any hard prompt can be turned into a soft prompt, but most soft prompts don't correspond to any hard prompt. Soft prompts can be tuned via gradient descent, for example.

Hard-prompt harnesses are hopelessly rigid. Worse, they tend to be filled with bad writing, which leads to bad simulations.