perf(api): load the discovery set once per location request

getCurrentLocation was calling isTravelAllowed per connection, re-querying
the character's discovered locations once per gated exit. Extract the
gating rule into a pure, synchronous WorldDiscoveryService.isRouteOpen so
the map filter can load the discovery set once and filter in memory, while
isTravelAllowed (TravelService's entry point) keeps its exact signature and
behaviour by delegating to the same rule. Also pins that discoversLocationKey
never reaches the client payload.

apps/api/src/world/discovery/world-discovery.service.ts

@@ -80,7 +80,24 @@ export class WorldDiscoveryService {
     }
 
     const known = await this.getDiscoveredLocationIds(characterId, manager);
-    return known.has(connection.toLocationId);
+    return this.isRouteOpen(known, connection);
+  }
+
+  /**
+   * The gating rule itself, given an already-loaded discovery set.
+   *
+   * Pure and synchronous so a caller with many connections can load the set
+   * once and filter in memory, while `isTravelAllowed` stays the convenient
+   * single-connection entry point. One rule, two callers.
+   */
+  isRouteOpen(
+    discoveredLocationIds: ReadonlySet<string>,
+    connection: Pick<LocationConnection, 'toLocationId' | 'requiresDiscovery'>,
+  ): boolean {
+    return (
+      !connection.requiresDiscovery ||
+      discoveredLocationIds.has(connection.toLocationId)
+    );
   }
 
   private discoveries(manager?: EntityManager) {

apps/api/src/world/world.service.spec.ts

@@ -56,6 +56,7 @@ const BURNED_ROAD_POIS: LocationPointOfInterestContent[] = [
     enabled: true,
     resultTitle: 'Suspicious Tracks',
     resultText: 'Fresh bootprints lead east.',
+    discoversLocationKey: 'ash-pit',
   },
   {
     key: 'sealed-crypt',
@@ -238,14 +239,15 @@ function buildService(
   } as unknown as Repository<LocationMonster>;
   const worldDiscovery = {
     discover: jest.fn(),
-    isTravelAllowed: (
-      _characterId: string,
+    getDiscoveredLocationIds: jest
+      .fn()
+      .mockResolvedValue(new Set(options.discovered ?? [])),
+    isRouteOpen: (
+      discoveredLocationIds: ReadonlySet<string>,
       connection: { toLocationId: string; requiresDiscovery: boolean },
     ) =>
-      Promise.resolve(
       !connection.requiresDiscovery ||
-          (options.discovered ?? []).includes(connection.toLocationId),
-      ),
+      discoveredLocationIds.has(connection.toLocationId),
   } as unknown as WorldDiscoveryService;
 
   const service = new WorldService(
@@ -307,7 +309,11 @@ describe('WorldService', () => {
       find: findLocationMonsters,
     } as unknown as Repository<LocationMonster>;
     const worldDiscovery = {
-      isTravelAllowed: () => Promise.resolve(true),
+      getDiscoveredLocationIds: jest.fn().mockResolvedValue(new Set()),
+      isRouteOpen: (
+        _discoveredLocationIds: ReadonlySet<string>,
+        connection: { requiresDiscovery: boolean },
+      ) => !connection.requiresDiscovery,
       discover: jest.fn(),
     } as unknown as WorldDiscoveryService;
     const service = new WorldService(
@@ -395,7 +401,11 @@ describe('WorldService', () => {
       find: findLocationMonsters,
     } as unknown as Repository<LocationMonster>;
     const worldDiscovery = {
-      isTravelAllowed: () => Promise.resolve(true),
+      getDiscoveredLocationIds: jest.fn().mockResolvedValue(new Set()),
+      isRouteOpen: (
+        _discoveredLocationIds: ReadonlySet<string>,
+        connection: { requiresDiscovery: boolean },
+      ) => !connection.requiresDiscovery,
       discover: jest.fn(),
     } as unknown as WorldDiscoveryService;
     const service = new WorldService(
@@ -436,7 +446,11 @@ describe('WorldService', () => {
       find: findLocationMonsters,
     } as unknown as Repository<LocationMonster>;
     const worldDiscovery = {
-      isTravelAllowed: () => Promise.resolve(true),
+      getDiscoveredLocationIds: jest.fn().mockResolvedValue(new Set()),
+      isRouteOpen: (
+        _discoveredLocationIds: ReadonlySet<string>,
+        connection: { requiresDiscovery: boolean },
+      ) => !connection.requiresDiscovery,
       discover: jest.fn(),
     } as unknown as WorldDiscoveryService;
     const service = new WorldService(
@@ -514,6 +528,8 @@ describe('WorldService', () => {
     ]);
     expect(JSON.stringify(result)).not.toContain('Fresh bootprints');
     expect(JSON.stringify(result)).not.toContain('Still sealed');
+    expect(JSON.stringify(result)).not.toContain('discoversLocationKey');
+    expect(JSON.stringify(result)).not.toContain('ash-pit');
   });
 
   it('derives the encounter preview from the location monster pool', async () => {
@@ -620,7 +636,11 @@ async function loadLocation(
       find: jest.fn().mockResolvedValue(pool),
     } as unknown as Repository<LocationMonster>,
     {
-      isTravelAllowed: () => Promise.resolve(true),
+      getDiscoveredLocationIds: jest.fn().mockResolvedValue(new Set()),
+      isRouteOpen: (
+        _discoveredLocationIds: ReadonlySet<string>,
+        connection: { requiresDiscovery: boolean },
+      ) => !connection.requiresDiscovery,
       discover: jest.fn(),
     } as unknown as WorldDiscoveryService,
   );

apps/api/src/world/world.service.ts

@@ -87,15 +87,16 @@ export class WorldService {
       ? await this.getEncounterPool(location.id)
       : [];
 
-    const visibleConnections: LocationConnection[] = [];
-    for (const connection of connections) {
-      if (
+    // Loaded once per request rather than per connection: `isRouteOpen` is
+    // synchronous, so a location with several gated exits costs one query
+    // here instead of one per gated connection.
+    const discoveredLocationIds =
+      await this.worldDiscovery.getDiscoveredLocationIds(characterId);
+    const visibleConnections = connections.filter(
+      (connection) =>
         connection.enabled &&
-        (await this.worldDiscovery.isTravelAllowed(characterId, connection))
-      ) {
-        visibleConnections.push(connection);
-      }
-    }
+        this.worldDiscovery.isRouteOpen(discoveredLocationIds, connection),
+    );
 
     return {
       id: location.id,