Every display test answered the controller with a hand-written stub, and
every viewer test called the service with a hand-written object, so
neither side was ever tested against the other. In production every
heartbeat was refused with a 400.
This suite answers the real controller's requests with the real viewer
route handlers over the in-memory store. The routes gain an optional
store factory for that; production still uses the module database.
Fails today: POST /viewers/:viewerId/heartbeat -> 400
SIGNAGE_INVALID_REQUEST, because the display sends
reportedContributionId: null and the route accepts only a missing field.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
