fix(game): recover realtime dashboard delta cloning

app/game-frontend/test/readModelDeltaRecovery.test.ts

@@ -0,0 +1,42 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import { resolveWithReadModelSnapshotFallback } from '../src/utils/readModelDeltaRecovery.ts';
+
+void test('retries any local delta application failure once with a forced snapshot', async () => {
+    const requests: boolean[] = [];
+    const result = await resolveWithReadModelSnapshotFallback({
+        request: async (forceSnapshot) => {
+            requests.push(forceSnapshot);
+            return forceSnapshot ? { kind: 'snapshot', value: 25 } : { kind: 'patch', value: 20 };
+        },
+        resolve: (response) => {
+            if (response.kind === 'patch') {
+                throw new DOMException('[object Object] could not be cloned.', 'DataCloneError');
+            }
+            return response.value;
+        },
+    });
+
+    assert.equal(result, 25);
+    assert.deepEqual(requests, [false, true]);
+});
+
+void test('does not retry a forced snapshot application failure', async () => {
+    const requests: boolean[] = [];
+
+    await assert.rejects(
+        resolveWithReadModelSnapshotFallback({
+            forceSnapshot: true,
+            request: async (forceSnapshot) => {
+                requests.push(forceSnapshot);
+                return { kind: 'snapshot' };
+            },
+            resolve: () => {
+                throw new Error('snapshot failure');
+            },
+        }),
+        /snapshot failure/u
+    );
+    assert.deepEqual(requests, [true]);
+});