Context Extraction Service

High level Requirements:

• Strong focus on performance: KV-level initial response speeds.
• For each link in the prompt, the frontend should have an api to render the context card for it which includes {url, title, tokens, ogImage, contentType, ...other}. these should be dynamically rendered below your prompt, and must be clear which belongs to which url somehow. when a prompt is pre-loaded, context cards may be pre-loaded from head JSON
• Get the appropriate context for showing "context-cards" as well as for building context
• Sanetize/DOMPurify?
• Structured response: Invdividual URLs (url => object), but also think about string => array
• Possibly separate in 2 apis: per item and for entire string.
• ability to omitContext to just get details for api.

TODO

1. Make this work as embeddable worker lib
2. Use this in pastebin demo.html instead of doing the fetch in there (risking cors or other different results)
3. Make demo into a js-lib (contextarea.js) so the HTML has full control over styling and page composition.
4. In api, add result to window.data.context: object[]
5. In both homepage.html and result.html use contextarea.js