v0.10.0

feat: add external asset prefixing and persisted run results

- add build/serve asset prefix support for static asset URLs
- generate static-files.txt for rewritten asset references
- add Wrangler helper for uploading listed assets to R2
- resolve relative asset paths from the page directory
- persist executable code block results back into Markdown
- render saved text, Markdown, and Codex results inline
- update MathJax loading to lazy v4 initialization
- document external asset and R2 upload workflows