Fix exitStagingMode for rehydrated containers

When a container is rehydrated from pending state while in staging mode,
the DataObject doesn't have stageControls (only set when enterStagingMode
is called). Handle this gracefully by returning early instead of asserting.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Co-Authored-By: anthony-murphy <anthony.murphy@microsoft.com>

Author: 3 people

packages/test/local-server-stress-tests/src/stressDataObject.ts

@@ -314,7 +314,12 @@ export class DefaultStressDataObject extends StressDataObject {
 	}
 
 	public exitStagingMode(commit: boolean): void {
-		assert(this.stageControls !== undefined, "must have staging mode controls");
+		// If stageControls is undefined but we're in staging mode, this means
+		// the container was rehydrated from pending state while in staging mode.
+		// We can't exit staging mode from here - skip gracefully.
+		if (this.stageControls === undefined) {
+			return;
+		}
 		if (commit) {
 			this.stageControls.commitChanges();
 		} else {