test: cover the successful travel start happy path in the e2e smoke suite

The DB-gated e2e suite covered health, seeded reads, and the arrivesAt
whitelist rejection, but never asserted that a valid POST /api/travel
actually transitions to TRAVELLING, that a concurrent second start is
rejected with 409/TRAVEL_ALREADY_ACTIVE, or that a travel completes and
moves the character. Added one test covering all three plus GET
/api/world/current-location reflecting the move, and restores the demo
character to its original location afterward so the suite stays safely
re-runnable.

apps/api/test/visible-slice.e2e-spec.ts

@@ -152,5 +152,104 @@ describe('Visible vertical slice smoke (e2e)', () => {
         })
         .expect(400);
     });
+
+    it(
+      'POST /api/travel starts a travel, rejects a concurrent start, and completes into the moved character (full happy path)',
+      async () => {
+        // `GET current-location` lazily completes any overdue travel left
+        // behind by a previous run before we read the starting point, so
+        // this test is safe to re-run without a fresh seed.
+        const origin = await request(app.getHttpServer())
+          .get('/api/world/current-location')
+          .expect(200);
+        const originLocationId: string = origin.body.id;
+        const outbound = origin.body.connections[0];
+        const targetLocationId: string = outbound.targetLocation.id;
+        const travelDurationSeconds: number = outbound.travelDurationSeconds;
+
+        const started = await request(app.getHttpServer())
+          .post('/api/travel')
+          .send({ targetLocationId })
+          .expect(201);
+
+        expect(started.body).toMatchObject({
+          status: 'TRAVELLING',
+          targetLocation: { id: targetLocationId },
+        });
+        expect(typeof started.body.arrivesAt).toBe('string');
+        expect(Number.isNaN(Date.parse(started.body.arrivesAt))).toBe(false);
+
+        const concurrentStart = await request(app.getHttpServer())
+          .post('/api/travel')
+          .send({ targetLocationId })
+          .expect(409);
+        expect(concurrentStart.body).toMatchObject({
+          code: 'TRAVEL_ALREADY_ACTIVE',
+        });
+
+        const arrivedTravel = await pollUntilTravelCompletes(
+          app,
+          travelDurationSeconds,
+        );
+        expect(arrivedTravel).toMatchObject({
+          status: 'COMPLETED',
+          targetLocation: { id: targetLocationId },
+        });
+
+        const arrivedLocation = await request(app.getHttpServer())
+          .get('/api/world/current-location')
+          .expect(200);
+        expect(arrivedLocation.body.id).toBe(targetLocationId);
+
+        // Restore the demo character to its original location so the suite
+        // (and this test) stays safely re-runnable.
+        const returnConnection = arrivedLocation.body.connections.find(
+          (connection: { targetLocation: { id: string } }) =>
+            connection.targetLocation.id === originLocationId,
+        );
+        expect(returnConnection).toBeDefined();
+
+        await request(app.getHttpServer())
+          .post('/api/travel')
+          .send({ targetLocationId: originLocationId })
+          .expect(201);
+
+        const returnedTravel = await pollUntilTravelCompletes(
+          app,
+          returnConnection.travelDurationSeconds,
+        );
+        expect(returnedTravel).toMatchObject({
+          status: 'COMPLETED',
+          targetLocation: { id: originLocationId },
+        });
+
+        const restoredLocation = await request(app.getHttpServer())
+          .get('/api/world/current-location')
+          .expect(200);
+        expect(restoredLocation.body.id).toBe(originLocationId);
+      },
+      30_000,
+    );
+
+    async function pollUntilTravelCompletes(
+      application: INestApplication<App>,
+      travelDurationSeconds: number,
+    ): Promise<{ status: string; targetLocation?: { id: string } }> {
+      const deadline = Date.now() + travelDurationSeconds * 1000 + 5_000;
+      let body: { status: string; targetLocation?: { id: string } };
+
+      do {
+        const response = await request(application.getHttpServer())
+          .get('/api/travel/current')
+          .expect(200);
+        body = response.body;
+        if (body.status === 'COMPLETED') {
+          return body;
+        }
+        await new Promise((resolve) => setTimeout(resolve, 500));
+      } while (Date.now() < deadline);
+
+      return body;
+    }
   });
 });