Continue conversation with tool task update

Updates a tool task and continues the conversation if appropriate. This endpoint:

1. Optionally updates the tool task with provided data (if request body is provided)
2. Checks if the tool task state requires AI continuation (input-required, completed, failed)
3. If the entry is the last entry in the discussion and AI continuation is needed, streams the AI response
4. Otherwise, returns the discussion entry with updated tool task information

This is the preferred endpoint for frontend applications that want to update tool tasks and potentially trigger AI responses.