test(catalog-backend): await engine start/stop in integration test harness

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Fredrik Adelöw <freben@gmail.com>

plugins/catalog-backend/src/tests/integration.test.ts

@@ -360,12 +360,12 @@ class TestHarness {
     const tracker = new WaitingProgressTracker(entityRefs);
     this.#proxyProgressTracker.setTracker(tracker);
 
-    this.#engine.start();
+    await this.#engine.start();
     await this.#stitcher.start();
 
     const errors = await tracker.wait();
 
-    this.#engine.stop();
+    await this.#engine.stop();
     await tracker.waitForFinish();
 
     // Wait for the stitch queue to drain while the stitcher is still running