feat: grammar-aware i18n module extracted from core
Standalone grammar-aware translation engine with:
- 3-tier verb/noun fallback (JSON locale → irregular maps → regular rules)
- 6 built-in i18n.* namespace handlers (label, progress, count, done, fail, numeric)
- Nested en.json with gram/prompt/time/lang sections (no flat command keys)
- CLDR plural rules for 10 languages
- Subject fluent API, number/time formatting, RTL detection
- 55 tests passing
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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