[codex] redesign Everything CodeX handbook layout

[tidus2005]

What changed

• Reworked the handbook into a v2 draft with a stronger commercial-handbook reading flow.
• Added four visual assets under assets/v2/: operating system map, surface map, delivery loop, and 90-day roadmap.
• Added reproducible scripts for image generation and PDF rendering.
• Regenerated docs/Everything-CodeX.pdf as a clearer A4 Markdown-like PDF.

Validation

• Rendered docs/Everything-CodeX.pdf successfully with 27 pages.
• Checked PDF pages 1-4, 20, 22, 24, and 27 visually from rendered PNGs.
• Verified PDF text extraction with pypdf.
• Ran Python syntax check for the new scripts.
• Ran secret-pattern scan across docs, scripts, assets, README, and LICENSE with no matches.
• Ran git diff --cached --check clean before commit.

Review notes

• This PR intentionally focuses on layout, visual hierarchy, PDF rendering, and graphic assets.
• Xiaohongshu publishing is not included in this PR because local browser automation could not access a controllable Chrome/Safari window in the current desktop session.