Story 2.3: Re-graft the retriever + bump langchain-arangodb
requested to merge bmad-loop/20260812-175834-e897/2-3-re-graft-the-retriever-bump-langchain-arangodb into feat/opea-1.5-upgrade/prd
Trace MR created by bmad-loop story-track.
Trace MR created by bmad-loop story-track.