chore: import upstream snapshot with attribution

showcase/integrations/langgraph-python/qa/threadid-frontend-tool-roundtrip.md

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+# Thread ID Frontend Tool Round Trip
+
+## Scope
+
+Regression checklist for ENT-658: a `CopilotChat` wrapped by
+`CopilotChatConfigurationProvider` must keep its SDK-generated non-explicit
+thread active across a frontend tool call and follow-up run.
+
+## Manual QA
+
+- [ ] Navigate to `/demos/threadid-frontend-tool-roundtrip`.
+- [ ] Verify the chat input is visible and `Explicit threadId` is unchecked.
+- [ ] Send `invoke testFrontendToolCalling with label X`.
+- [ ] Verify the user message remains visible.
+- [ ] Verify the `testFrontendToolCalling` card remains visible and shows
+      `label: X` and `result: handled X`.
+- [ ] Verify the assistant reply `Frontend tool finished for X.` appears.
+- [ ] Verify the chat does not return to the empty state.
+- [ ] Refresh the page or open a new tab, check `Explicit threadId` before
+      sending any message, send the same prompt again, and verify the same
+      message/tool/reply persistence behavior.
+- [ ] Optionally toggle `Explicit threadId` after a generated-thread
+      conversation and verify the chat switches to the explicit thread's
+      history. An empty explicit thread on first use is expected.
+
+## Automated Coverage
+
+- `tests/e2e/threadid-frontend-tool-roundtrip.spec.ts` covers the demo route,
+  generated-thread default state, and explicit-thread toggle.
+- `packages/react-core/src/v2/components/chat/__tests__/CopilotChat.absentThreadConnect.test.tsx`
+  covers the SDK-generated thread handoff at the component level.