Support diffs

Right now, we generate the full code each time. It would be better to generate diffs and patch those diffs in

Here is some good [prompt inspiration](https://github.com/paul-gauthier/aider/blob/main/aider/coders/udiff_prompts.py) for doing this

We did a brief try at this before, but without a good prompt. Trying again could really save on tokens and increase execution speed

No project file, test, or entry point is named in the issue. Start by reviewing the existing code-generation flow and the linked aider/coders/udiff_prompts.py example; the work is done when the agent generates diffs, applies those diffs, and reduces token use and execution time.

Written by the indexing model from the issue text.