~anthropic/claude-sonnet-latest → B (75:25)

Side B is a real bugfix: it moves the zero-ratio guard before ensure_item/voted_pairs insertion, preventing ghost items and incorrectly-marked voted pairs, and updates the test to verify the corrected behavior. Side A is purely mechanical file-splitting (moving code from one forum.rs into multiple forum/*.rs submodules) with no behavioral change, so while it improves organization, it carries less lasting substantive value than a genuine correctness fix.