chore: fix operation over cdp (#440)

Ref https://github.com/microsoft/playwright-mcp/issues/439

src/pageSnapshot.ts

@@ -40,6 +40,9 @@ export class PageSnapshot {
   }
 
   private async _build() {
+    // FIXME: Rountrip evaluate to ensure _snapshotForAI works.
+    // This probably broke once we moved off locator snapshots
+    await this._page.evaluate(() => 1);
     const snapshot = await callOnPageNoTrace(this._page, page => (page as PageEx)._snapshotForAI());
     this._text = [
       `- Page Snapshot`,