chore: import upstream snapshot with attribution

showcase/integrations/claude-sdk-python/qa/open-gen-ui-advanced.md

@@ -0,0 +1,38 @@
+# QA: Open-Ended Generative UI (Advanced) — Claude Agent SDK (Python)
+
+## Prerequisites
+
+- Demo is deployed and accessible
+- Agent backend is healthy
+- ANTHROPIC_API_KEY is set
+
+## Test Steps
+
+### 1. Basic Functionality
+
+- [ ] Navigate to `/demos/open-gen-ui-advanced`
+- [ ] Click the "Calculator (calls evaluateExpression)" suggestion
+- [ ] Verify an iframe renders with a calculator UI (no <form>, only <button type='button'>)
+
+### 2. Sandbox-Function Round-Trip
+
+- [ ] In the calculator, enter "12 \* (3 + 4.5)" and press "="
+- [ ] Verify the display updates with the host-evaluated result
+- [ ] Open devtools console — verify `[open-gen-ui/advanced] evaluateExpression` log appears
+
+### 3. notifyHost
+
+- [ ] Try the "Ping the host (calls notifyHost)" suggestion
+- [ ] Click the button in the rendered card
+- [ ] Verify `[open-gen-ui/advanced] notifyHost:` log in the host console
+- [ ] Verify the card updates with a confirmation showing `receivedAt`
+
+### 4. Error Handling
+
+- [ ] Verify no CORS/CSP errors from the sandbox
+- [ ] Verify evaluateExpression rejects non-arithmetic input safely
+
+## Expected Results
+
+- Sandbox -> host calls via Websandbox.connection.remote work end-to-end
+- Handler return values are visible inside the iframe UI