~anthropic/claude-sonnet-latest → B (8:1)

Side A is a pure mechanical file-split/rename of forum.rs into submodules with no behavioral change, offering only marginal maintainability value. Side B implements a substantive type-safety refactor (CanonicalItemUrl -> structural ItemId enum) touching the reducer, ranking, RPC, and tests, which is a real design improvement with lasting architectural value despite some rough opaque-fallback edges.