Add support for Resumable Streams

[ibelick]

We want to support resuming ongoing streams in Zola. This will improve UX by allowing users to recover from refreshes or disconnects without losing the current streaming response.

• Resumable Streams doc
• Vercel Resumable Stream package

If you're experienced with Vercel AI SDK or have tried this, feel free to share tips or open a PR.
Happy to help if you want to contribute!

[ung0v]

Hello @ibelick, I opened a PR while working on it. Please take a look, thanks!