Implement debounced async autocomplete input

Implement an autocomplete input component from scratch. Requirements: 1) Debounce user keystrokes to avoid excessive network calls. 2) Perform asynchronous fetches for suggestions; handle loading, errors, and empty results; prevent stale responses from overwriting newer ones. 3) Render a suggestions list under the input with proper focus management. 4) Support keyboard navigation: Up/Down arrows move the active index, the active option is visually highlighted, and Enter selects/submits the active option. 5) Describe your event-handler and state design (what states you keep, how they transition, and how you wire input, list, and keyboard events).