feat: Add Traditional Chinese (zh-TW) i18n support

[sd0xdev]

Summary

Adds full internationalization (i18n) infrastructure and Traditional Chinese (zh-TW) translation for the entire project — game UI, course lessons, and documentation.

• i18n engine: New strings.js with detectLocale(), t() dual-signature helper, T.* template functions, and localizeHTML() — locale detected via ?lang=zh-TW URL parameter
• Game fully localized: All room descriptions, item names, enemy names, NPC dialogues, UI buttons, status text, and combat messages translated to zh-TW with inline _zh suffix fields in data JSON files
• 11 course lessons translated: Complete zh-TW lesson files in learn-claude/zh-TW/, with lesson metadata (title_zh, file_zh) in lessons.json
• Course locale support: /course lang zh-TW command to switch course language, stored in course-progress.json
• Translation quality: Reviewed with adversarial brainstorming (Claude + Codex) for Taiwan-native conventions — oral tone for game UI, English retained for gaming terms (HP, Session), consistent 的 naming style for items, monster language kept in original English
• CJK typography: Dedicated font stack (Noto Sans TC, PingFang TC, Microsoft JhengHei) with adjusted font sizes (14px base vs 10px pixel font) and antialiasing for Chrome/Safari
• Server bug fix: req.url with query string (e.g. /?lang=zh-TW) caused 404 — fixed by stripping query params before file path resolution (affects dungeon/, reference/complete/, reference/starter/)
• Test suite: 86 tests (82 i18n + 4 server) covering t() behavior, T.* templates, data file integrity (_zh fields), S string completeness, dirNames, and server query string routing
• Unified scripts: pnpm start runs complete game (both languages), pnpm run dev runs student workspace

Files Changed

New Files

File	Description
reference/complete/strings.js	i18n engine — locale detection, translation helpers, string maps, template functions
learn-claude/zh-TW/*.md (11 files)	Traditional Chinese translations of all course lessons
README.zh-TW.md	Traditional Chinese README
tests/i18n.test.js	i18n unit tests (82 tests)
tests/server.test.js	Server routing tests (4 tests)
vitest.config.js	Test configuration
package.json	Project scripts and dependencies

Modified Files

File	Changes
reference/complete/game.js	Use t() / T.* for all user-facing strings; take()/talk() match zh-TW names
reference/complete/ui/ui.js	Localized UI updates, encounter stats, item icons
reference/complete/style.css	CJK font stack, adjusted sizes for zh-TW readability
reference/complete/index.html	Include strings.js
reference/complete/data/*.json	Added _zh fields and icon fields to all data files
reference/complete/server.js	Strip query string from URL path; zh-TW log message
reference/starter/server.js	Strip query string from URL path
dungeon/server.js	Strip query string from URL path; zh-TW log message
.claude/skills/course/SKILL.md	Added `lang en
.claude/skills/course/lessons.json	Added title_zh, file_zh, name_zh fields
CLAUDE.md	Added i18n section documenting architecture and conventions
README.md	Added pnpm start/pnpm run dev scripts, language commands

i18n Architecture

URL ?lang=zh-TW
       │
       ▼
  detectLocale()  →  locale = "zh-TW"
       │
       ├──▶ t(S.welcome)         →  "歡迎來到 Dungeons & Agents！"
       ├──▶ t(room, "name")      →  room.name_zh
       ├──▶ T.youGo("up")        →  "你往上走。"
       └──▶ T.localizeExits(...) →  "上、下"

Test Plan

• pnpm test — 86 tests pass
• Open http://localhost:3000 — English UI renders correctly
• Open http://localhost:3000?lang=zh-TW — Chinese UI renders with correct fonts/sizes
• Run /course lang zh-TW then /course — dashboard shows Chinese lesson titles
• In zh-TW: take, talk, attack commands work with Chinese item/NPC names
• Server starts with both EN and zh-TW URLs in console log