Add tests for locale file structure and completeness:
- Test languages.json has required fields (zh, en labels, llmInstruction)
- Test zh/en translations have common keys (confirm, cancel, etc.)
- Test zh and en have same top-level keys
- Test translation interpolation format ({var} placeholders)
- Test existing translation files have consistent structure
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>