gpt: convert ChatGPT web conversations to dialogs

[kafkasl]

![WARNING] DRAFT: This is a bit of a prompt request attempt. I would like this feature to be available and this shape works for me but I haven't reviewed the code carefully in case we don't want this merged.

This PR adds support to convert a ChatGPT convo (from the browser) to a dialog.

The flow is:

1. Open it in ChatGPT and click Share to create a link.
2. Pass that link (or the live /c/ URL) to url2convo
3. convo2dlg turns the payload into a dialog, one prompt per user turn.

The tool assumes you can reach the payload. For a public share link that's a plain GET with no login.

Tests run against a real captured conversation, data/gpt/hugo.json, curated like the oai rollouts.

Decisions

I am not sure what the best shape to retrieve the page is. Fetching needs a browser context (like fastcdp) for two reasons: Cloudflare blocks non-browser clients such as httpx for any conversation, public or private; and private or workspace conversations additionally need the logged-in session's token.

I would like this to be pretty "smooth", you just give the URL and the tool can handle it. I have added an example using fastcdp and explained how to do it manually. LLMs should also be able to use other tech like playwright instead of fastcdp from the example.

[kafkasl]

Moved this feature into its own repo as agreed https://github.com/AnswerDotAI/chatgpt2dlg