feat(i18n): add Korean (ko) locale

[YeonghyeonKO]

Summary

• Adds ko / 한국어 to SUPPORTED_LANGUAGES in src/frontend/src/constants/languages.ts and src/frontend/src/i18n.ts
• Adds i18n.changeLanguage(lang) after addResourceBundle in loadLanguage so the UI re-renders immediately when the lazy bundle finishes loading
• Adds src/frontend/src/locales/ko.json with 2,228 translated strings covering every key in en.json

The locale file follows the same flat-key structure used by all other locale files (fr, ja, zh-Hans, etc.).

Rebased onto current main

This branch has been rebased onto current main. ko.json was regenerated against the latest en.json:

• +178 keys translated — the strings added since the branch was opened: a11y labels (feat: a11y #13561, fix(a11y): label icon-only controls #13678, fix(frontend): clear /flows page a11y debt #13891, fix(a11y): improve API keys tab order #13953, fix(a11y): make /assets/files accessible #13987, fix(a11y): add accessible names to notifications popover controls #13994, fix(a11y): fix traces page accessibility violations — rowgroup tabbable #13744, fix(a11y): resolve WCAG 2.1 Level A and AA violations on settings general page #13811), the A2A agent tab (feat(a2a): A2A protocol support #13831), durable execution / HITL (feat: durable background execution + HITL suspend/resume schema #13633, fix(hitl): rename inputs, advanced timeout + HITL palette and control polish #14090), the inspector→parameter-manager rework (feat(frontend): turn inspector panel into a parameter manager #14078), Azure AI Foundry deployment names (fix(models): allow Azure AI Foundry deployment names instead of catalog IDs #14023), and the modifier-only shortcut guard (fix(frontend): reject modifier-only keyboard shortcuts #14187)
• −12 stale keys dropped — keys removed upstream, plus two entries that no longer existed in en.json

Verification

• Key set is identical to en.json (2,228 keys, no missing and no extra)
• Key order matches en.json
• Every {{interpolation}} placeholder and <1>…</1> Trans tag matches the corresponding English string exactly (0 mismatches)
• Plural forms (_one / _other) are present for all counted strings, matching the convention used by the other locale files

[coderabbitai]

Walkthrough

Korean (ko / 한국어) is added to the SUPPORTED_LANGUAGES constant and to the normalizeLanguage allowlist in i18n.ts. Additionally, loadLanguage is updated to call i18n.changeLanguage(lang) after registering a non-English locale bundle.

Changes

Korean language support and i18n activation fix

Layer / File(s)	Summary
Korean registration and language activation fix src/frontend/src/constants/languages.ts, src/frontend/src/i18n.ts	Adds { code: "ko", label: "한국어" } to SUPPORTED_LANGUAGES, adds "ko" to the normalizeLanguage supported codes, and adds i18n.changeLanguage(lang) call in loadLanguage after a non-English locale bundle is imported and registered.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 6 | ❌ 3

❌ Failed checks (3 warnings)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Test Quality And Coverage	⚠️ Warning	No tests added for Korean language support. New i18n functionality (i18n.changeLanguage call) and Korean locale loading not tested; existing tests use mocks instead of validating actual behavior.	Add tests to i18n.test.ts verifying loadLanguage('ko') loads the bundle successfully and i18n.changeLanguage is called; verify all translation keys present.
Test File Naming And Structure	⚠️ Warning	PR adds Korean language support but lacks corresponding test coverage. No new tests were added to verify the Korean locale loads correctly, that the added i18n.changeLanguage() call works properly,...	Add tests for Korean language: test that ko.json loads successfully, verify i18n.changeLanguage() is called in loadLanguage(), test normalizeLanguage() accepts 'ko', and add parametrized/data-driven tests for supported languages.

✅ Passed checks (6 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding Korean locale support to the i18n system.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Test Coverage For New Implementations	✅ Passed	PR includes comprehensive test coverage for new functionality: 2 frontend i18n test files (3+5 tests) covering loadLanguage and changeLanguage behavior, 1 component test file (8 tests) covering Lan...
Excessive Mock Usage Warning	✅ Passed	This PR adds Korean language support (locale configuration, translation file, and UI re-render fix). No test files were added or modified in this PR, making the mock usage check not applicable.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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