feat(analyze): detect closed vocabulary drift

[AnkitPorwal04]

Summary

• inventory explicitly named finite sets during semantic modeling
• compare repeated declarations and report their symmetric member difference
• avoid false positives for documented subsets and unnamed example lists
• expose a closed-vocabulary mismatch metric in the analysis report
• add a focused command-template contract test

Fixes #4106

Testing

• .venv\Scripts\python.exe -m pytest tests\test_analyze_closed_vocabulary.py tests\test_specify_template_numbering.py -q (3 passed)
• git diff --check

AI assistance disclosure

This pull request was implemented, tested, and drafted autonomously by OpenAI Codex (GPT-5) on behalf of @AnkitPorwal04. The human operator selected the overall goal but did not line-by-line author or review the patch before submission.