Address review: consistent v2 API, unique thread_id, SDK prereq note

Author: DABH

langgraph_plugin/README.md

@@ -19,6 +19,8 @@ Samples are organized by API style:
 
 ## Prerequisites
 
+> **Note:** These samples require the LangGraph plugin from [sdk-python#1448](https://github.com/temporalio/sdk-python/pull/1448), which has not been released yet. They will not be runnable until the SDK is published with the `temporalio[langgraph]` extra.
+
 1. Install dependencies:
 
    ```bash

langgraph_plugin/graph_api/human_in_the_loop/workflow.py

@@ -60,7 +60,9 @@ def get_draft(self) -> str | None:
     @workflow.run
     async def run(self, user_message: str) -> str:
         g = graph("chatbot").compile(checkpointer=InMemorySaver())
-        config = RunnableConfig({"configurable": {"thread_id": "1"}})
+        config = RunnableConfig(
+            {"configurable": {"thread_id": workflow.info().workflow_id}}
+        )
 
         # First invocation: runs generate_draft, then pauses at interrupt()
         result = await g.ainvoke(user_message, config, version="v2")
@@ -72,4 +74,7 @@ async def run(self, user_message: str) -> str:
         await workflow.wait_condition(lambda: self._human_input is not None)
 
         # Resume the graph with the human's feedback
-        return await g.ainvoke(Command(resume=self._human_input), config)
+        resumed = await g.ainvoke(
+            Command(resume=self._human_input), config, version="v2"
+        )
+        return resumed.value