Do not mandate, demonstrate. Put Heidi in the busiest channel, let people see real questions get real sourced answers, and redirect repeat questions to her visibly. Usefulness in the open is the whole adoption strategy.
Working in the open is the adoption engine: every answer someone sees teaches the room what Heidi can do, which private-tab AI can never achieve. The morning briefing and weekly reports create daily proof without anyone changing habits.
One or two enthusiasts matter more than a rollout plan. Give the person who loves this stuff the keys in Heidi Control, and let their delegation habits spread by envy.