Langroid

chainlit: show_first_user_message() to display first user message when it's not yet part of an agent loop

DocChatAgent.ingest_doc_paths -> return list[Document] not None

Fix chainlit logging

Chainlit support via callbacks. Two ways to use these:
* if interacting directly with a `ChatAgent`, use `ChainlitAgentCallbacks(agent)` to inject callbacks into the Agent.
* if using a `Task`, use `ChainlitTaskCallbaks(task)` to recursievely inject callbacks into the task's Agent and those of any sub-tasks.

Callbacks here: https://github.com/langroid/langroid/blob/main/langroid/agent/callbacks/chainlit.py

See extensive examples here: https://github.com/langroid/langroid/tree/main/examples/chainlit

Uptate litellm -> 1.20.6 (fixes bugs, incl dropping API params)

None