Fetch a web page URL and convert it to clean Markdown optimized for LLM context. Preserves headings, code blocks (with language hints), links, and tables; strips ads, navigation, and cookie banners. For Mintlify docs (docs.anthropic.com, OpenAI platform, Vercel, Stripe, etc.) tries the URL.md convention first for cleanest output. Discovers tab groups statically and emits each panel as a ### Tab: {label} section instead of concatenating (prevents Python+TypeScript examples merging into one broken block). Zero external API calls — parses locally via linkedom.