Implement production-grade linguistic logic in UniversalLinguisticEngine

Replaced mock data and placeholders with:
- Extensive rule-based PhoneticEngine handling digraphs, silent E, and vowel teams.
- Expanded ConstraintGrammar with a rich lexicon and proper feature-based generation.
- Implemented grammatical logic for Number Agreement (Det-N, Subj-Verb) and Transitivity.
- Added verification logic to ensure no regression.

Author: google-labs-jules[bot]