chore: import upstream snapshot with attribution

showcase/integrations/langgraph-python/qa/declarative-hashbrown.md

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+# QA: Declarative UI — Hashbrown — LangGraph (Python)
+
+## Prerequisites
+
+- Demo deployed at `/demos/declarative-hashbrown`
+- Railway service `showcase-langgraph-python-production` healthy
+- `OPENAI_API_KEY` set in the Railway environment
+- `@hashbrownai/core` + `@hashbrownai/react` installed in the package
+- `byoc_hashbrown` graph registered in `langgraph.json`
+
+## Test Steps
+
+### 1. Page load
+
+- [ ] Navigate to `/demos/declarative-hashbrown`
+- [ ] Header "Declarative UI: Hashbrown" visible
+- [ ] Short description mentioning `@hashbrownai/react` visible
+- [ ] Chat composer visible at the bottom of the chat area
+- [ ] 3 suggestion pills visible inside the composer with labels:
+      "Sales dashboard", "Revenue by category", "Expense trend"
+- [ ] No red console errors (amber hydration warnings tolerated)
+
+### 2. Sales dashboard suggestion
+
+- [ ] Click the "Sales dashboard" pill
+- [ ] The prompt is dispatched automatically (useConfigureSuggestions sends
+      the message on pill click)
+- [ ] Within 45 seconds, at least one MetricCard (`data-testid="metric-card"`)
+      renders in the transcript
+- [ ] Within 45 seconds, at least one chart
+      (`data-testid="bar-chart"` or `data-testid="pie-chart"`) renders
+- [ ] Rendered content streams progressively — partial UI appears before the
+      full response completes (optional visual check)
+
+### 3. Revenue by category
+
+- [ ] Click "Revenue by category"
+- [ ] Within 45s, a pie chart (`data-testid="pie-chart"`) renders
+- [ ] Legend shows at least 4 segments with readable labels and values
+
+### 4. Expense trend
+
+- [ ] Click "Expense trend"
+- [ ] Within 45s, a bar chart (`data-testid="bar-chart"`) renders
+- [ ] Chart has at least 3 bars with month-like labels
+
+### 5. Free-form prompt
+
+- [ ] Type "Show me revenue trends for the last six months" and press Enter
+- [ ] Verify at least one catalog component renders (metric, chart, or deal)
+
+### 6. Multi-turn
+
+- [ ] After a first render completes, send a follow-up prompt
+      (e.g. "Now break it down by region")
+- [ ] A new render appears alongside prior renders in the transcript
+
+### 7. Error handling
+
+- [ ] Empty send is a no-op (button stays disabled)
+- [ ] Console remains clean during successful flows
+
+## Expected Results
+
+- Suggestion pills produce a hashbrown render within 45 seconds
+- Streaming renders assemble progressively as JSON chunks arrive
+- No uncaught errors; no `useHashBrownKit must be used within
+HashBrownDashboard` errors
+- Multi-turn works without clearing prior renders