Build an AI second brain and research clipper web app. Features: 1) Web clipper: save articles, web pages, and snippets with a browser extension or paste URL, 2) PDF import: upload research papers and PDFs, AI extracts key sections, abstracts, and references, 3) AI annotation: highlight text and AI generates summaries, questions, and connections to other saved items, 4) Smart search: semantic search across all saved content, ask questions and get AI-synthesized answers with citations to your sources, 5) Knowledge graph: AI automatically links related items and shows connections between concepts, 6) Tags and collections: organize saved items with tags, collections, and AI-suggested categories, 7) Reading queue: a queue of saved items to read later with AI-generated TLDR for each, 8) Export: export notes and annotations as Markdown or PDF, 9) Sync across devices: mobile-first responsive design with offline support for saved items. Use a clean, scholarly UI with a reading pane, annotation sidebar, and a knowledge graph visualization.