~x-ai/grok-latest → B (2:5)

B replaces the old composable ParsedUrl/engine normalizers and domain_key match arms with a graph-based canonicalization API (registry thin wrapper over graph/parse, docs and tests re-homed), which is lasting core ItemId design. A mostly deletes the leftover monolithic forum.rs and redistributes the same forum HTML into forum/* modules plus a small timeago import fix—necessary structure cleanup, but little new behavior or design.