- extract_outline_entries: filter PDF bookmarks by depth and major structural headings, avoiding 550 micro-snippets
- renderContinuousBook: load current chapter and seamlessly append next chapters on scroll (virtual continuous) instead of dumping all chapters into DOM synchronously
- renderInteractiveSpans: use native HTML template fragment instead of new DOMParser per paragraph
- event delegation: handle word clicks on readerContentBody instead of adding hundreds of thousands of individual DOM event listeners
- consolidate existing CCNA book in DB into 68 clean chapters