Can agent support stream and async？

[bianchenhao]

For combinine shinychat.
Now, agent can only invoke, like code below, not a good interactive experience.

library(shiny)
library(shinychat)

ui <- bslib::page_fillable(
  chat_ui(
    id = "chat",
    messages = "**Hello!** How can I help you today?"
  ),
  fillable_mobile = TRUE
)

server <- function(input, output, session) {
  
  observeEvent(input$chat_user_input, {
    stream <- r_assistant$invoke(input$chat_user_input)
    chat_append("chat", stream)
  })
}

shinyApp(ui, server)

And LeadAgent is not async now, I can't capture intermediate state which I want to show users in shinychat.

[selesnow]

Very useful and well-designed package — the agent abstraction on top of ellmer is excellent.

However, there is currently no direct integration with the shinychat package, which makes it harder to use mini007 in Shiny-based chat interfaces.

Even a minimal or officially recommended mini007 + shinychat integration would be a big improvement.