Markdown to Slug: turn a heading into a stable address

Parse Markdown and extract visible text instead of removing syntax with a broad regex; links, code spans, entities and nested emphasis otherwise leave artifacts. Normalize Unicode, choose a documented transliteration policy, lowercase consistently, collapse separators, and trim to a safe length without cutting an encoded character. Slugs need collision handling and reserved-name checks. Once published, treat the slug as stable: changing normalization rules should create a redirect rather than silently breaking existing links.