Fine-grained Markdown

Code Hike introduces 'fine-grained markdown' — a way to break markdown content into structured, named blocks that can be individually accessed and rendered with React. By annotating headings and elements with special decorators, content authors can define blocks like `intro` and `steps`, which are then parsed and destructured in code. A Zod-based schema system adds TypeScript autocompletion and runtime validation, so missing required elements (like a cover image) produce clear errors. This approach gives developers full control over how structured markdown content is presented using React components.