Inventory entries can have stars=null or discovered_at=null. Replace
.get("stars", 0) with .get("stars") or 0 in all three modules so that
None values are safely coerced to 0/"" before numeric/string comparison.
Fixes TypeError crashes in:
- v2_optimizer.py:632 _calculate_tags
- dedup.py:74,108 title dedup and entry scoring
- news_digest.py:322 category pool sorting
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>