Add TreeWork web paper reader and clarify product positioning

[Johnny-xuan]

Summary

• add a responsive Web Paper reader generated from the authoritative LaTeX sources
• provide chapter navigation, full-paper search, reading settings, themes, citation tools, formula rendering, and figure lightboxes
• keep reading progress in the Contents rail and expose the PDF and GitHub repository from the reader toolbar
• describe TreeWork publicly as a tree-guided development plugin while retaining state-native project memory as the paper's theoretical framing

Why

The repository currently exposes the paper primarily as a PDF. This reader makes the paper easier to navigate and inspect while keeping the LaTeX document as the source of truth. The product-facing copy now leads with what users and coding agents actually do: organize work as a tree and move through it without losing direction.

Validation

• npm run build
• git diff --check
• desktop, tablet, and mobile layout checks in the Codex in-app browser
• verified formulas, search, reading settings, responsive navigation, and zero browser console errors