v4.50.0

Changed

• The HU Board is always kj's board, and your tracker gets the replica (KJC-BUG-0305, #2042): with the Planning Game or an external board (Linear, Jira, Trello...), kj hu add and kj hu move used to refuse, and kj told agents never to keep a parallel HU Board. Now the HU Board records every card on every backend, kj hu add --ref <id> links the card's replica in your tracker (kj hu list shows it), the method asks for both cards, and the Steward cards broken invariants on the HU Board, naming where to replicate them.
• Card-first checks the HU Board with an external tracker too (KJC-BUG-0353): a live HU the branch names, by its own id or by its replica's id, passes at hu-board level instead of a mere check of the reference's shape. A tracker reference no HU links still passes, with the remedy in the note.