feat: Turkish translation

[Ardakilic]

Turkish Language Support

Summary

Added Turkish ("tr") localization support to CodeIsland, following the existing pattern for English (en) and Chinese (zh). Users can now select Turkish as their preferred language in settings, and the app will detect Turkish as the system language when the macOS locale is set to Turkish.

Changes

Modified Files

1. Sources/CodeIsland/L10n.swift

   • Added "tr" to the supported languages dictionary
   • Added Turkish translation dictionary with ~110 key-value pairs covering all UI strings
   • Updated effectiveLanguage to detect Turkish system locale

2. Sources/CodeIsland/SettingsView.swift

   • Added Turkish ("Türkçe") option to the language picker

3. Sources/CodeIsland/Settings.swift

   • Updated comment to include "tr" in the appLanguage values

Added Files

1. Tests/CodeIslandTests/L10nTests.swift
   • Unit tests for Turkish localization coverage
   • Tests for language detection, fallback behavior, and numeric placeholders

Testing

New tests verify:

• Turkish translations contain all keys present in English
• Turkish language returns correct translations
• All language options work correctly
• Numeric placeholders work in Turkish

Breaking Changes

None. This is a backward-compatible enhancement.

Notes

• Turkish translations follow macOS Turkish UI conventions
• Language picker displays the native language name "Türkçe"
• System locale detection supports "tr" prefix