feat(sync): round trip cloud snapshots

cloudflare/tests/index.test.ts

@@ -359,6 +359,10 @@ function testEnv(
       get(key: string): Promise<string | null> {
         return Promise.resolve(values.get(key) ?? null);
       },
+      put(key: string, value: string): Promise<void> {
+        values.set(key, value);
+        return Promise.resolve();
+      },
       delete(key: string): Promise<void> {
         values.delete(key);
         return Promise.resolve();