Build a Streaming Chat Input

Implement a simple front-end chat interface similar to a minimal AI assistant. Requirements: - Show a text input and a submit button. - When the user submits a prompt, call a provided API that returns the assistant response as a stream of text chunks. - Render the streamed response below the input as chunks arrive, rather than waiting for the full response. - Keep the UI responsive while the stream is in progress. - Prevent or handle duplicate submissions while a response is streaming. - Display basic loading and error states. You may assume the API endpoint and response-streaming format are provided by the interviewer. Focus on the component structure, state management, and streaming-render behavior.