chore: import upstream snapshot with attribution

showcase/integrations/claude-sdk-python/qa/hitl-in-app.md

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+# QA: In-App HITL — Claude Agent SDK (Python)
+
+## Prerequisites
+
+- Demo is deployed and accessible
+- Agent backend is healthy (check /api/health)
+- ANTHROPIC_API_KEY is set
+
+## Test Steps
+
+### 1. Basic Functionality
+
+- [ ] Navigate to `/demos/hitl-in-app`
+- [ ] Verify the Support Inbox renders three tickets (#12345, #12346, #12347)
+- [ ] Verify the chat surface renders on the right
+
+### 2. Approval Flow
+
+- [ ] Click the "Approve refund for #12345" suggestion
+- [ ] Verify a modal dialog appears with the action summary
+- [ ] Click "Approve" — verify the dialog closes and the agent confirms
+
+### 3. Rejection Flow
+
+- [ ] Click the "Downgrade plan for #12346" suggestion
+- [ ] Verify the modal appears
+- [ ] Add a note "Customer needs to stay on current plan"
+- [ ] Click "Reject" — verify the agent acknowledges the rejection
+
+### 4. Error Handling
+
+- [ ] Verify no console errors during the approval/rejection flows
+- [ ] Verify the modal blocks interaction with the chat until resolved
+
+## Expected Results
+
+- Modal uses `fixed inset-0` overlay rather than a portal (to avoid @types/react-dom)
+- Agent accurately reflects the approve/reject outcome