[yangroro]

Summary

This PR adds Korean (ko) as a UI locale. It follows the Italian locale from #117 and uses the same per-locale lazy dictionary registry.

Localization

• Adds ko to Locale / ALL_LOCALES. A browser language of ko* now defaults to Korean, <html lang> is set to ko, and the agent's response-language prompt says Korean.
• The top bar language button cycles 中 → EN → IT → RU → 한 and shows 한 when Korean is active.
• Adds src/i18n/dict/ko/. It uses the same per-domain split as dict/en (audio, captions, chat, components, editor, exportPanel, fx, library, media, review, settings, timeline, topbar, transcript), and index.ts assembles the files. Each ko/<field>.ts holds the keys of the matching en/<field>.ts in the same order. The EN files generate / progress / script are intentionally empty, so they have no Korean counterpart.
  • It covers all 2,496 English UI entries. Two more keys are used in source through context.t() but have no EN entry yet (切换 WebCodecs…, 素材「{name}」已存在。…). Their Korean entries sit in exportPanel.ts / media.ts.
  • ko/templates-data.ts covers all 304 data display names: the 24 Chinese-key names for self-made templates (en/templates-data) and the 280 English-key names for built-in templates, sounds and music (zh/templates|sounds|music).
• Translation approach: English was the source of truth and the Chinese original was a cross-reference. Every entry was reviewed in a second pass. The same Chinese key can appear in several places (as a menu title and as a sentence fragment), so each key has one Korean string that fits all of its uses.
• Fallback: ko UI copy falls back to English, then to the Chinese key (uiFallback: EN). Data names fall back to EN_DATA, the same wiring as it. A string added to EN before Korean catches up shows in English, not Chinese.
• Server-side copy:
  • localized() in server/ui-locale.ts accepts an optional ko variant and falls back to English. No server message has a ko variant yet, so they all show in English for Korean users, the same as Italian today.
  • The phone upload page (server/mobile-upload-service.ts) gets a full Korean copy, and ?locale=ko is accepted.
• Transcription language selectors already list Korean (韩语（ko）), so settingsMediaProviders.ts is unchanged.

Out of scope

• Template propSchema field labels are English in the original source for every locale, so they stay as they are.
• Font names are proper names and are not translated.
• Hard-coded English fallbacks in src/agent/toolFailure.ts / serverRunToolEnvironment.ts (handled for zh/ru only) show English for ko, the same as it.

Verification

New executable check:

• src/i18n/dict/ko/coverage.verify.ts, wired into npm run verify:i18n. It asserts that every EN key has a non-empty Korean entry, that every Korean entry has the same {placeholder} set as its EN entry (or as the Chinese key when EN has none), and that every data name in EN_DATA + ZH_DATA has a Korean display name.

Extended checks:

• src/i18n/locale.verify.ts: switching to ko persists cc.locale=ko and sets <html lang="ko">.
• src/i18n/dictRegistry.verify.ts: ko reads KO, translates both Chinese-key and English-key data names, and is wired to EN / EN_DATA as fallbacks.
• src/agent/systemPromptOrder.verify.ts: the ko response-language prompt names Korean.
• server/mobile-upload-service.verify.ts: a ko session serves <html lang="ko"> with Korean copy.
• server/plugins/mobile-upload.verify.ts: ?locale=ko reaches createSession('ko').

Commands:

• npm run lint: passes (exit 0; warnings only, all pre-existing)
• npm test: passes, 197/197 segments (631 registered verify files, including pretest verify:i18n and posttest)
• npm run build: tsc -b and vite build pass, and so do the other prebuild steps (sync-shader-sources --check, sync:mediapipe, verify:server-tool-catalog). On the macOS machine used here, prebuild's sync:whisper-cli stops before compiling because cmake is not installed (cmake is required to build whisper.cpp). That step is environment-dependent and does not touch this change; CI runs the full npm run build.
• Korean is emitted as its own lazy chunk (ko-*.js, ~202 kB / 72 kB gzip), so it does not grow the entry chunk.

scripts/verify-gate-coverage.verify.mjs exempts src/i18n/dict/ko/settings.ts (531 lines) from the 500-line source limit, the same as en/settings.ts. It mirrors en/settings.ts key for key and holds only dictionary data.

Screenshots

Web mode with localStorage['cc.locale'] = 'ko'.

Home (project list)

Editor (example project)

Top bar language button (한)

Settings

Export dialog

Captions panel

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