chore: import upstream snapshot with attribution

showcase/integrations/claude-sdk-python/qa/frontend-tools.md

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+# QA: Frontend Tools — 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/frontend-tools`
+- [ ] Verify a chat surface renders in the centered card
+- [ ] Send a message: "Change the background to a blue-to-purple gradient."
+- [ ] Verify the agent calls the `change_background` frontend tool
+- [ ] Verify the page background updates to the requested gradient
+
+### 2. Feature-Specific Checks
+
+- [ ] Click the "Sunset theme" suggestion — background changes to a sunset gradient
+- [ ] Ask "Change the background back to default." — background resets
+- [ ] Verify no errors in the console
+
+### 3. Error Handling
+
+- [ ] Verify the chat remains usable after multiple background changes
+
+## Expected Results
+
+- Background element with `data-testid="background-container"` reflects the CSS background value returned by the tool handler
+- Agent calls the tool and produces a short confirmation message