Add message action buttons (copy, feedback, regenerate, share)

[JamesHWade]

Feature Request

Add optional action buttons to assistant messages for common interactions:

• Copy: Copy message content to clipboard
• Feedback: Thumbs up/down for rating responses
• Regenerate: Request a new response
• Share: Share the message

Usage

chat_ui("chat", message_actions = TRUE)
# or specific actions:
chat_ui("chat", message_actions = c("copy", "feedback"))

chat_ui("chat", message_actions=True)
# or specific actions:
chat_ui("chat", message_actions=["copy", "feedback"])

Events are exposed as Shiny inputs (R: input$ID_message_feedback, Python: @chat.on_message_feedback decorator).

Screenshot

Draft PR

https://github.com/JamesHWade/shinychat/pull/new/feature/message-action-buttons