🤖 fix: highlight TypeDoc API reference by processing nested chapters

- Fix preprocessor to handle nested sub-items correctly
- Sub-items are Section objects { Chapter: {...} }, not direct chapters
- Configure TypeDoc to use code blocks instead of inline code
- Added useCodeBlocks, expandObjects, and format options to typedoc.json
- Now highlights all 25 code blocks in API reference
- Fixes poor rendering of type signatures

Author: ammar-agent