feat(i18n): add Korean (ko) locale

[dwhavi]

Summary

• Add Korean (ko) locale support with 230+ translated keys in src/i18n/ko.ts
• Register Korean locale in src/i18n/index.ts (code: ko, label: 한국어, dateLocale: ko-KR)
• Add Korean-specific test cases in tests/i18n/index.test.ts for locale resolution, dateLocale, and options

Changes

File	Change
src/i18n/ko.ts	New — Korean translation dictionary (230+ keys)
src/i18n/index.ts	Modified — Import ko, add to LOCALE_DEFINITIONS
tests/i18n/index.test.ts	Modified — Add Korean locale test assertions

Translation Notes

• Speech level: 해요체 (Polite) — friendly yet respectful tone matching the English source
• Emoji: All emoji preserved exactly as in en.ts
• Interpolation: All {variable} patterns preserved exactly
• MCP section: Left in English following de.ts/zh.ts precedent
• Command descriptions: Concise Korean (e.g., "서버 및 세션 상태", "새 세션 생성")

Usage

Set BOT_LOCALE=ko in .env to activate Korean UI.

Verification

• tsc --noEmit ✅
• vitest run ✅ 886/886 tests pass
• eslint --max-warnings=0 ✅
• tsc build ✅ dist/i18n/ko.js generated

[grinev]

@dwhavi thanks for PR, please update README and .env.example files

[grinev]

And also please add translations for mcps.* keys, they are in english