Scheduled integration runs set `LANGSMITH_TAGS` and `LANGSMITH_METADATA`
in `$GITHUB_ENV` (per #37615), but the LangSmith SDK does not read those
env vars natively, so the tags/metadata were silently dropped. A new
pytest plugin in `langchain-tests` bridges that gap by entering
`langsmith.run_helpers.tracing_context` for the duration of each
session.
