chore: import upstream snapshot with attribution

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

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+# QA: Open-Ended Generative UI — 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`
+- [ ] Verify the chat renders with minimal suggestions visible
+- [ ] Click the "3D axis visualization (model airplane)" suggestion
+- [ ] Verify a sandboxed iframe appears with the generated visualization
+
+### 2. Feature-Specific Checks
+
+- [ ] Verify the iframe contains SVG-based content (not div-stacks)
+- [ ] Try the "Quicksort visualization" suggestion — verify an animated bar sort renders
+- [ ] Verify the visualization is self-running (no user interaction needed)
+
+### 3. Error Handling
+
+- [ ] Verify no CORS/CSP errors in the console
+- [ ] Verify the sandbox iframe renders within the chat turn
+
+## Expected Results
+
+- Agent calls `generateSandboxedUi` once per turn
+- The runtime's OpenGenerativeUIMiddleware converts the call into activity events
+- The built-in renderer mounts the agent-authored HTML inside a sandbox