I want to create a Chrome extension called "YouTube AI Summarizer" that summarizes YouTube videos using AI (OpenAI API). Generate a complete feature list including core features, optional features, and UI/UX elements.

Consider:

Popup UI

Context menu option on YouTube

Auto-detecting video URL

Fetching captions or transcripts

Sending transcript to an AI model for summarization

Displaying summary in popup or a side panel

Options page for API key and settings

Browser notifications if needed

Handling errors gracefully

Give me a structured feature list with categories: Core Features, Optional Features, User Settings, and UI/UX.