Add Chinese (zh-CN) localization and adjust deployment metadata and workflow. Translated README and extensive src content to Chinese, updated book.toml (language, title, description, authors, git-repository-url, and edit-url-template pointing to translate/zh-cn), and switched the GitHub Pages deploy workflow to trigger on translate/**. Prepares the repo to host and deploy the zh-CN translation and route edit links to the translation branch.
- Add anchor links to every section reference across README,
repeatedly-changing-systems, and detailed-primers index
- Add Quick-Scan Class/Method Index table for compile-error lookup
- Add Entities/mobs/mob AI topic section to the topic map
- Surface all Minor Migrations subsections individually
- Nest primer pages under Detailed Primers in sidebar
- Enable search
- Replace CSS with cleaner dark theme (system fonts, GitHub palette)
- Remove direct-port-guide.md (21k line inlined primer merge)
- Remove duplicate Google Fonts import from head.hbs
