LangChainEnvMetadata returns filtered LANGCHAIN_/LANGSMITH_ env vars.
func LangChainEnvMetadata() map[string]anyLangChainEnvMetadata returns filtered LANGCHAIN_/LANGSMITH_ env vars suitable for merging into extra.metadata, with the revision env vars mapped to revision_id. The tracing client only uses this when WithMergeFilteredEnvIntoExtraMetadata(true) is set. The same map may be returned on each call; do not mutate it—copy first if you need to edit.