~anthropic/claude-sonnet-latest → B (8:2)

Side B is a substantial type-safety refactor that threads CanonicalItemUrl through resolve_item, RPC handlers, and validation, eliminating repeated string-to-newtype conversions and reducing the chance of stringly-typed bugs across a large surface area, plus adding Deref impls for ergonomics. Side A is a tiny, low-risk cleanup removing dead code with a corresponding test fix, which is correct but narrow in scope and impact compared to B's broader architectural improvement.