chore: import upstream snapshot with attribution

showcase/integrations/langgraph-python/src/agents/frontend_tools_async.py

@@ -0,0 +1,32 @@
+"""LangGraph agent backing the Frontend Tools (Async) demo.
+
+This cell demonstrates `useFrontendTool` with an ASYNC handler. The
+frontend registers a `query_notes` tool whose handler awaits a simulated
+client-side DB query (500ms latency) and returns matching notes. The
+agent uses the returned result to summarize what it found.
+
+Like the sibling `frontend_tools` cell, the backend graph registers no
+tools of its own — CopilotKit forwards the frontend tool schema(s) to
+the agent at runtime, and the handler executes in the browser.
+"""
+
+from langchain.agents import create_agent
+from langchain_openai import ChatOpenAI
+from copilotkit import CopilotKitMiddleware
+
+SYSTEM_PROMPT = (
+    "You are a helpful assistant that can search the user's personal notes. "
+    "When the user asks about their notes, call the `query_notes` tool with "
+    "a concise keyword extracted from their request. The tool is provided "
+    "by the frontend at runtime and runs entirely in the user's browser — "
+    "you do not need to implement it yourself. After the tool returns, "
+    "summarize the matching notes clearly and concisely. If no notes match, "
+    "say so plainly and offer to try a different keyword."
+)
+
+graph = create_agent(
+    model=ChatOpenAI(model="gpt-5.4"),
+    tools=[],
+    middleware=[CopilotKitMiddleware()],
+    system_prompt=SYSTEM_PROMPT,
+)