Update README to reflect recent updates
Add Claude support, update history format, better summary prompt

A large refactoring to support multiple backends with similar, but not identical, APIs. Backend selection is now done with `--backend={gpt4,claude}`, the `--api_key` parameter should point to the correct API key for the given service.

The history file has been changes from `titles` to `history`, and is now JSON-object-per-line formatted so that more metadata can be stored (e.g. which bot you chatted with)

The summary prompt has also been updated, as it didn't work well on Claude and frequently added "quotes" on both GPT-4 and Claude 3
Update deps, fix pasting, and "fix" long text issue

- Fix pasting by doing it manually
- Fix our long text bug out issue by just making lines arbitrarily short
Call out a few features
Add screenshots and update README
Initial Sourcehut commit, cleaned up history