feat: allow any valid ISO locale code in validation

[maxprilutskiy]

Summary

• Updates locale validation to accept any valid ISO-standard locale code instead of being restricted to a hardcoded list of ~222 locales
• Enables support for locale codes like en-NZ, de-LU, es-CO, ar-DZ, etc. that follow ISO standards but weren't previously in the hardcoded list
• Maintains backward compatibility with all existing tests

Changes

packages/spec/src/locales.ts

• Added import of isValidLocale from @lingo.dev/_locales package
• Updated localeCodeSchema to use comprehensive ISO standard validation instead of hardcoded list check
• Validation now uses normalization + ISO standards validation (184 language codes, 200+ script codes, 249 region codes)

packages/spec/package.json

• Added @lingo.dev/_locales as a workspace dependency

Validation Coverage

The updated validation accepts locales conforming to:

• ISO 639-1 language codes (2-letter, e.g., en, es, de)
• ISO 15924 script codes (4-letter, optional, e.g., Hans, Latn, Cyrl)
• ISO 3166-1 alpha-2 region codes (2-letter, optional, e.g., US, GB, CN)
• UN M.49 numeric region codes (3-digit, optional, e.g., 419 for Latin America)

Test Results

✅ All existing tests pass:

• packages/spec/src/locales.spec.ts - 14 tests passing
• packages/spec/src/config.spec.ts - 5 tests passing
• Full build succeeds across all packages

Manual Testing

Verified new locale codes are accepted:

• ✅ en-NZ (New Zealand English)
• ✅ de-LU (Luxembourg German)
• ✅ es-CO (Colombian Spanish)
• ✅ pt-AO (Angolan Portuguese)
• ✅ ar-DZ (Algerian Arabic)
• ✅ sr-Latn-ME (Serbian Latin Montenegro)
• ✅ uz-Cyrl-UZ (Uzbek Cyrillic)

Invalid codes are still rejected:

• ❌ invalid-XX
• ❌ xx-US
• ❌ en-ZZZZ

Benefits

1. Broader locale support: Users can now use any valid ISO locale code, not just the hardcoded ones
2. Standards-based: Validation follows ISO 639-1, ISO 15924, ISO 3166-1, and UN M.49 standards
3. Reduced maintenance: No need to manually add new locales to the hardcoded list
4. Backward compatible: All existing locale codes continue to work

Test Plan

• Run pnpm test in packages/spec
• Run pnpm -r build for full monorepo build
• Verify new locale codes are accepted
• Verify invalid locale codes are rejected
• Confirm all pre-commit hooks pass