Why: A1 - the cancel library command was declined as host-unconsumed, so "取消刚才的任务" could not act on a real run. Evidence: route/server/intentsession tests pass (verify-a1c.json); explicit-id, session-bound, ambiguous and cross-owner cases added; confirmation card semantics unchanged. Impact: cancel decisions dispatch via the existing host path; other intents unchanged. Refs: feature/intent-multi-turn-a1