~anthropic/claude-sonnet-latest → A (6:4)

Side A introduces a genuinely new, composable url_rules engine (ParsedUrl combinators + per-domain registry) with real behavior additions (YouTube canonicalization, tracking-param stripping, alias tracking) plus tests, replacing ad-hoc string canonicalization with a more maintainable design. Side B is a large but mostly mechanical rename/refactor (CanonicalItemUrl -> ItemId enum) that changes call sites and tests extensively without adding new normalization capability, and even removes a planning doc (plan.md) that documented intended future work, reducing net lasting value relative to its churn.