Support using Exa for webpage reading. It seems much faster than
currently available providers.
Remove Jina as a webpage reader and remaining references to Jina from
code, docs. It was anyway slow and API may shut down soon (as it was
bought by Elastic).
Update docs to mention Exa for web search and webpage reading.
Update offline, openai chat actor, director tests to not require
Serper to run the online command tests
Update documentation for self-hosted online search to mention no setup
is required by default. But improvements can be made by using
Serper.dev or Olostep
