Validate scene document during serialization and parsing

src/serialization/scene-document-json.ts

@@ -1,7 +1,9 @@
 import type { SceneDocument } from "../document/scene-document";
 import { migrateSceneDocument } from "../document/migrate-scene-document";
+import { assertSceneDocumentIsValid } from "../document/scene-document-validation";
 
 export function serializeSceneDocument(document: SceneDocument): string {
+  assertSceneDocumentIsValid(document);
   return JSON.stringify(document, null, 2);
 }
 
@@ -15,5 +17,7 @@ export function parseSceneDocumentJson(source: string): SceneDocument {
     throw new Error(`Scene document JSON could not be parsed: ${cause}`);
   }
 
-  return migrateSceneDocument(parsedValue);
+  const document = migrateSceneDocument(parsedValue);
+  assertSceneDocumentIsValid(document);
+  return document;
 }