Revert "chore(lgp): Remove langsmith runs endpoints env var" (#185)

Reverts #184

Author: angus-langchain

src/langgraph-platform/env-var.mdx

@@ -54,18 +54,13 @@ For example, if a deployment is scaled up to 10 replicas and `LANGGRAPH_POSTGRES
 
 Defaults to `150` connections.
 
-## `LANGSMITH_ENDPOINT`
-For deployments with [self-hosted LangSmith](https://docs.smith.langchain.com/self_hosting) only.
-
-Set this environment variable to have a deployment send traces to a self-hosted LangSmith instance.
+## `LANGSMITH_RUNS_ENDPOINTS`
 
- The value of `LANGSMITH_ENDPOINT` should be the hostname of the self-hosted LangSmith instance. It must be accessible to the deployment.
-
- You must also set `LANGSMITH_API_KEY` to the API key for the self-hosted LangSmith instance.
+For deployments with [self-hosted LangSmith](https://docs.smith.langchain.com/self_hosting) only.
 
-## `LANGSMITH_API_KEY`
+Set this environment variable to have a deployment send traces to a self-hosted LangSmith instance. The value of `LANGSMITH_RUNS_ENDPOINTS` is a JSON string: `{"<SELF_HOSTED_LANGSMITH_HOSTNAME>":"<LANGSMITH_API_KEY>"}`.
 
-`LANGSMITH_API_KEY` is a LangSmith API generated from the self-hosted LangSmith instance.
+`SELF_HOSTED_LANGSMITH_HOSTNAME` is the hostname of the self-hosted LangSmith instance. It must be accessible to the deployment. `LANGSMITH_API_KEY` is a LangSmith API generated from the self-hosted LangSmith instance.
 
 ## `LANGSMITH_TRACING`