test(display): run the real display controller against the real viewer routes

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]>

src/server/routes/viewers.ts

@@ -23,9 +23,11 @@ import {
 
 const OPAQUE_ID = /^[\w][\w.:-]{0,199}$/u;
 
-function store(context: ModuleRouteHandlerContext): SignageStore {
-  return createSignageStore(context.services.database);
-}
+/** How a route reaches Signage's tables. Production uses the module database; the display contract
+ * test supplies the in-memory store so the real handlers can answer the real display controller. */
+export type ViewerRouteStore = (context: ModuleRouteHandlerContext) => SignageStore;
+
+const databaseStore: ViewerRouteStore = (context) => createSignageStore(context.services.database);
 
 /**
  * The safe Core device identifier, when the caller is a paired display.
@@ -57,6 +59,7 @@ export function registerViewerRoutes(
   http: ModuleHttpRouteRegistrar,
   playback: () => SignagePlaybackService,
   registry: () => SignageProviderRegistry,
+  store: ViewerRouteStore = databaseStore,
 ): void {
   http.route({
     method: "POST",