v4.5.0

Minor. Any board — but always a board. Projects that already live in Linear, Trello, Jira or GitHub Issues get card-first pointed at THEIR board; and no project runs without one (closes #1287).

Added

• External boards as source of truth (KJC-TSK-0684): state_backend: external + board.name make the playbook's card-first invariant point at the project's own board, worked through the host agent's MCP/tools. kj never mirrors it: kj hu add|move refuse with the pointer, kj board doesn't start a parallel dashboard (stop stays available for cleanup). Default hu-board unchanged.
• kj env install guarantees an operational board (KJC-TSK-0685): hu-board is ok by construction (it ships with kj); planning-game requires its MCP in a host agent config; external requires the named board's MCP or an API token (per-board convention or board.token_env). No access path → PENDING-USER-ACTION block (exit 3) with the exact steps, before the RAG step. There is no none: Karajan does not run without a board — the board is what guarantees ordered, card-first work and meaningful lanes.