- Add Welcome section and "What You Will Build" list to preface
- Add TinyTorch link (mlsysbook.ai/tinytorch) in preface
- Add Unicode character support for arrows, math symbols, Greek letters
- Remove number prefixes from module chapter headings (01. → just title)
- Update PDF TOC to use pdf_intro.md as root with Getting Started as part
- Update TinyTorch-Guide.pdf and TinyTorch-Paper.pdf in downloads
- Remove duplicate tinytorch-course.pdf from downloads
