Add ko-KR, ko-KR-x-busan, and ja-JP-x-oita locales to i18n

[Copilot]

This PR adds three new locales to the internationalization (i18n) system:

Added Locales

1. ko-KR (Korean)

Base Korean locale with translations and fallback to en-US. Includes Korean translation for the "undo-closed-tab" feature:

• Label: "닫은 탭 다시 열기"

2. ko-KR-x-busan (Korean - Busan dialect)

Regional variant for the Busan dialect with fallback to ko-KR. Currently uses an empty translation object to leverage the fallback chain, ready for future dialect-specific translations.

3. ja-JP-x-oita (Japanese - Oita dialect)

Regional variant for the Oita dialect with fallback to ja-JP. Currently uses an empty translation object to leverage the fallback chain, ready for future dialect-specific translations.

Structure

Each locale directory follows the established pattern:

i18n/
├── ko-KR/
│   ├── _meta.toml           # Fallback configuration: ["en-US"]
│   ├── browser-chrome.json  # Korean translations
│   └── default.json         # Empty object for future use
├── ko-KR-x-busan/
│   ├── _meta.toml           # Fallback configuration: ["ko-KR"]
│   ├── browser-chrome.json  # Empty object (uses fallback)
│   └── default.json         # Empty object for future use
└── ja-JP-x-oita/
    ├── _meta.toml           # Fallback configuration: ["ja-JP"]
    ├── browser-chrome.json  # Empty object (uses fallback)
    └── default.json         # Empty object for future use

Fallback Chain

The locales implement proper fallback chains:

• ko-KR → en-US → dev
• ko-KR-x-busan → ko-KR → en-US → dev
• ja-JP-x-oita → ja-JP → en-US → dev

This ensures users always see appropriate translations even when dialect-specific translations are not available.

Implementation Notes

• The existing config.ts uses import.meta.glob which automatically discovers and loads these new locale directories
• Regional variants without distinct translations use empty objects to properly leverage the fallback system
• All JSON files are properly formatted and validated
• Structure is consistent with existing locales (en-US, ja-JP, ja-JP-x-kansai)

Original prompt

add ko-KR, ko-KR-x-busan, ja-JP-x-oita to i18n

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