Debug and extend a streaming chat app

## Scenario You are given a small codebase for a web chat UI that calls an LLM API (similar to a ChatGPT-style interface). You can run it locally. During a 60-minute interview, you must **debug issues and implement small features**. Assume a typical setup: - Frontend chat UI (e.g., React/Vue) with a client-side store/state management layer. - A backend (or direct client call) that invokes an LLM API. - Responses may be **streamed** token-by-token. ## Tasks ### Bug 1: API key invalid When starting the app and sending a message, the browser console (or network response) shows an error like **`api key invalid`**. - Find the root cause. - Fix the configuration so requests authenticate correctly. ### Bug 2: Message renders as empty After submitting a message, the UI receives a response but renders **empty content**. - Inspect the response payload. - Fix the parsing/rendering logic so the assistant text displays correctly. ### Feature 1: Add a **Clear** button Add a button that clears: - the visible message history - any stored conversation context - and resets the chat state to an initial empty state You are told the store already has an action/helper that can reset/initialize state—use it rather than re-implementing. ### Feature 2: Add a **Stop** button for streaming Add a button (like the “stop generating” square icon) that, while an assistant response is streaming, **immediately stops/cancels** the in-flight stream and leaves the partially-generated text as-is (or per your chosen UX, but be consistent). Consider: - state management changes (e.g., `isStreaming`, `currentRequestId`) - request cancellation (e.g., `AbortController`) - cleanup so future messages still work ## What we are evaluating - Your debugging workflow (repro, isolate, verify) - Correctness of fixes - Practical state management and cancellation handling - Ability to reason about API contract mismatches (payload shape vs. assumptions)