Simplify chat working indicator to dots-and-time text

[rexlManu]

Summary

• Simplifies the chat working indicator UI in ChatView to a minimal dots-and-time text treatment.
• Removes the bordered/background container styling for the indicator row.
• Removes the bot icon block from the working indicator, reducing visual noise.

Testing

• Not run (no runtime checks were provided in the change context).
• Verify in the chat UI that the working indicator now renders only animated dots with time text.
• Confirm accessibility behavior remains intact (role="status", aria-live="polite").