~anthropic/claude-sonnet-latest → B (3:1)

Side B fixes a real UI bug (unranked siblings were incorrectly lumped into one group instead of shown as separate isolated groups) and adds a regression test validating the corrected behavior. Side A is a pure mechanical file-splitting refactor (breaking up forum.rs into forum/*.rs modules) with no behavioral change or bug fix, offering organizational value but less lasting substantive impact than B's correctness fix plus test coverage.